<PAGE>

                                                                    EXHIBIT 10.8

 
                                PROMISSORY NOTE
                                ---------------


                                                                 LOAN NO. 240737
$1,610,000.00                        Dated to be effective as of October 8, 1997

                                                                   Dallas, Texas

     FOR VALUE RECEIVED, the undersigned, NEI REAL ESTATE, INC., a Texas
corporation ("Borrower"), whose address is 4646 Bronze Way, Dallas, Texas
              --------                                                    
75236, jointly and severally, if more than one, promises to pay to the order of
COLUMN FINANCIAL, INC., a Delaware corporation ("Lender"), at the office of
                                                 ------                    
Lender at 3414 Peachtree Road, N.E., Suite 1140, Atlanta, Georgia 30326-1113, or
at such other place as Lender may designate to Borrower in writing from time to
time, the principal sum of ONE MILLION SIX HUNDRED TEN THOUSAND AND NO/100
DOLLARS ($1,610,000.00), together with interest on so much thereof as is from
time to time outstanding and unpaid, from the date of the advance of the
principal evidenced hereby, at the rate of eight and 19/100 percent (8.19%) per
annum (the "Note Rate"), in lawful money of the United States of America, which
            ---------                                                          
shall at the time of payment be legal tender in payment of all debts and dues,
public and private.


                        ARTICLE I - TERMS AND CONDITIONS
                        --------------------------------

     Section 1.1    Payment of Principal and Interest.  Said interest shall be
                    ---------------------------------                         
computed hereunder based on a 360-day year but calculated on the actual number
of days in each calendar month.  In computing the number of days during which
interest accrues, the day on which funds are initially advanced shall be
included regardless of the time of day such advance is made, and the day on
which funds are repaid shall be included unless repayment is credited prior to
close of business.  Payments in federal funds immediately available in the place
designated for payment received by Lender prior to 2:00 p.m. local time at said
place of payment shall be credited prior to close of business, while other
payments may, at the option of Lender, not be credited until immediately
available to Lender in federal funds in the place designated for payment prior
to 2:00 p.m. local time at said place of payment on a day on which Lender is
open for business.  Such principal and interest shall be payable in equal
consecutive monthly installments of $12,629.56 each, beginning on the first day
of the second full calendar month following the date of this Promissory Note
(the "Note") (or on the first day of the first full calendar month following the
      ----                                                                      
date hereof, if the date of the advance of the principal amount evidenced by
this Note is the first day of a calendar month), and continuing on the first day
of each and every month thereafter until November 1, 2007 (the "Maturity Date"),
                                                                -------------   
at which time the entire outstanding principal balance hereof, together with all
accrued but unpaid interest thereon, shall be due and payable in full.  Each
such monthly installment shall be applied first to the payment of accrued
interest and then to reduction of principal.  If the advance of the principal
amount evidenced by this Note is made on a date other than the first day of a
calendar month, then Borrower shall pay to Lender contemporaneously with the
execution hereof interest at the Note Rate 

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for a period from the date hereof through and including the last day of the
calendar month in which this Note is funded.

     Section 1.2    Prepayment.
                    ---------- 

          (a) Prior to the Lockout Expiration Date (defined below), this Note
     may not be prepaid, either in whole or in part; provided, however, Borrower
     shall have the right and option to release the Security Property (as
     hereinafter defined) from the lien of the Security Instrument  (as
     hereinafter defined) in accordance with the terms and provisions of Section
     1.36 of the Security Instrument.  This Note may be prepaid in whole but not
     in part (except as otherwise specifically provided herein) at any time
     after the date six (6) months prior to the Maturity Date (the "Lockout
                                                                    -------
     Expiration Date") provided (i) written notice of such prepayment is
     ---------------                                                    
     received by Lender not more than sixty (60) days and not less than thirty
     (30) days prior to the date of such prepayment (ii) such prepayment is
     received on the first day of a calendar month (or, if such prepayment is
     not received on the first day of a calendar month, interest is paid through
     the last day of such calendar month) and is accompanied by all interest
     accrued hereunder and all other sums due hereunder or under the other Loan
     Documents and (iii) all indebtedness evidenced by that certain Promissory
     Note dated of even date herewith executed by NEI 4647, Inc. in the amount
     of $1,090,000.00 and made payable to Lender, is simultaneously paid in
     full.

          (b) If prior to the Lockout Expiration Date and following the
     occurrence of any default beyond any applicable notice and/or grace period,
     Borrower shall tender payment of an amount sufficient to satisfy all of the
     indebtedness evidenced by the Note and the other Loan Documents (as
     hereinafter defined) at any time prior to a sale of the Security Property,
     either through foreclosure or the exercise of the other remedies available
     to Lender under the Security Instrument, such tender by Borrower shall be
     deemed to be voluntary and Borrower shall pay, in addition to the amounts
     payable hereunder and under the Loan Documents, a prepayment fee in an
     amount equal to the greater of (A) two percent (2.0%) of the principal
     amount being prepaid, and (B) one percent (1%) of the principal amount
     being prepaid plus the positive excess of (i) the present value of all
     future installments of principal and interest due under this Note including
     the principal amount due at maturity, discounted at an interest rate per
     annum equal to the rate published in the Treasury Constant Maturity Yield
     Index, during the second full week preceding the date on which such premium
     is payable, for instruments having a maturity coterminous with the
     remaining term of this Note, over (ii) the principal amount of this Note
     outstanding immediately before such prepayment. "Treasury Constant Maturity
                                                      --------------------------
     Yield Index" shall mean the average yield for "This Week" as reported by
     -----------                                                             
     the Federal Reserve Board in Federal Reserve Statistical Release H.15
     (519).  If there is no Treasury Constant Maturity Yield Index for
     instruments having a maturity coterminous with the remaining term of this
     Note, then the index shall be equal to the weighted average yield to
     maturity of the Treasury Constant Maturity Yield Indices with maturities
     next longer and shorter than such remaining average life to maturity,
     calculated by averaging (and rounding upward to the nearest whole multiple
     of 1/100 of 1% per annum, if the average is 

                                                                   -------------
PROMISSORY NOTE - Page 2                                                Initials
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     not such a multiple) the yields of the relevant Treasury Constant Maturity
     Yield Indices (rounded, if necessary, to the nearest 1/100 of 1% with any
     figure of 1/200 of 1% or above rounded upward). In the event that any
     prepayment fee is due hereunder, Lender shall deliver to Borrower a
     statement setting forth the amount and determination of the prepayment fee,
     and, provided that Lender shall have in good faith applied the formula
     described above, Borrower shall not have the right to challenge the
     calculation or the method of calculation set forth in any such statement in
     the absence of manifest error, which calculation may be made by Lender on
     any day during the thirty (30) day period preceding the date of such
     prepayment. Lender shall not be obligated or required to have actually
     reinvested the prepaid principal balance at the Treasury Constant Maturity
     Yield Index or otherwise as a condition to receiving the prepayment fee.

          (c) Partial prepayments of this Note shall not be permitted, except
     partial prepayments resulting from Lender applying insurance or
     condemnation proceeds to reduce the outstanding principal balance of this
     Note as provided in the Security Instrument, in which event no prepayment
     fee or premium shall be due.  No notice of prepayment shall be required
     under the circumstance specified in the preceding sentence.  No principal
     amount repaid may be reborrowed.  Partial payments of principal shall be
     applied to the unpaid principal balance evidenced hereby but such
     application shall not reduce the amount of the fixed monthly installments
     required to be paid pursuant to Section 1.1 above.
                                     -----------       

     Section 1.3    Security.  The indebtedness evidenced by this Note and the
                    --------                                                  
obligations created hereby are secured by that certain Deed of Trust and
Security Agreement (the "Security Instrument") from Borrower to a trustee for
                         -------------------                                 
the benefit of Lender, dated of even date herewith, concerning property located
in Dallas County, Texas.  The Security Instrument together with this Note and
all other documents to or of which Lender is a party or beneficiary now or
hereafter evidencing, securing, guarantying, modifying or otherwise relating to
the indebtedness evidenced hereby, are herein referred to collectively as the
                                                                             
"Loan Documents".  All of the terms and provisions of the Loan Documents are
---------------                                                             
incorporated herein by reference.  Some of the Loan Documents are to be filed
for record on or about the date hereof in the appropriate public records.

     Section 1.4    Default.  It is hereby expressly agreed that should any
                    -------                                                
default occur in the payment of principal or interest as stipulated above and
such payment is not made within five (5) days of the date such payment is due
(provided that no grace period is provided for the payment of principal and
interest due on the Maturity Date), or should any other default occur under any
of the Loan Documents which is not cured within any applicable grace or cure
period, then a default shall exist hereunder, and in such event the indebtedness
evidenced hereby, including all sums advanced or accrued hereunder or under any
other Loan Document, and all unpaid interest accrued thereon, shall, at the
option of Lender and without notice to Borrower, at once become due and payable
and may be collected forthwith, whether or not there has been a prior demand for
payment and regardless of the stipulated date of maturity.  In the event that
any payment is not received by Lender on the date when due (subject to the
applicable grace period), then in addition to any default interest payments due
hereunder, at Lender's election, Borrower shall also pay to Lender a late charge
in an 

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amount equal to five percent (5.0%) of the amount of such overdue payment.
So long as any default exists hereunder, regardless of whether or not there has
been an acceleration of the indebtedness evidenced hereby, and at all times
after maturity of the indebtedness evidenced hereby (whether by acceleration or
otherwise), interest shall accrue on the outstanding principal balance of this
Note at a rate per annum equal to four percent (4.0%) plus the interest rate
which would be in effect hereunder absent such default or maturity, or if such
increased rate of interest may not be collected under applicable law, then at
the maximum rate of interest, if any, which may be collected from Borrower under
applicable law (the "Default Interest Rate"), and such default interest shall be
                     ---------------------                                      
immediately due and payable.  Borrower acknowledges that it would be extremely
difficult or impracticable to determine Lender's actual damages resulting from
any late payment or default, and such late charges and default interest are
reasonable estimates of those damages and do not constitute a penalty.  The
remedies of Lender in this Note or in the Loan Documents, or at law or in
equity, shall be cumulative and concurrent, and may be pursued singly,
successively or together, in Lender's discretion.  Time is of the essence of
this Note.  In the event this Note, or any part hereof, is collected by or
through an attorney-at-law, Borrower agrees to pay all costs of collection,
including, but not limited to, reasonable attorneys' fees.

     Section 1.5    Exculpation.  Notwithstanding anything in the Loan Documents
                    -----------                                                 
to the contrary, but subject to the qualifications hereinbelow set forth, Lender
agrees that (i) Borrower shall be liable upon the indebtedness evidenced hereby
and for the other obligations arising under the Loan Documents to the full
extent (but only to the extent) of the security therefor, the same being all
properties (whether real or personal), rights, estates and interests now or at
any time hereafter securing the payment of this Note and/or the other
obligations of Borrower under the Loan Documents (collectively, the "Security
                                                                     --------
Property"), (ii) if default occurs in the timely and proper payment of all or
--------                                                                     
any part of such indebtedness evidenced hereby or in the timely and proper
performance of the other obligations of Borrower under the Loan Documents, any
judicial proceedings brought by Lender against Borrower shall be limited to the
preservation, enforcement and foreclosure, or any thereof, of the liens,
security titles, estates, assignments, rights and security interests now or at
any time hereafter securing the payment of this Note and/or the other
obligations of Borrower under the Loan Documents, and confirmation of any sale
under power of sale, and no attachment, execution or other writ of process shall
be sought, issued or levied upon any assets, properties or funds of Borrower
other than the Security Property, except with respect to the liability described
below in this section, and (iii) in the event of a foreclosure of such liens,
security titles, estates, assignments, rights or security interests securing the
payment of this Note and/or the other obligations of Borrower under the Loan
Documents, whether by judicial proceedings or exercise of power of sale, no
judgment for any deficiency upon the indebtedness evidenced hereby shall be
sought or obtained by Lender against Borrower, except with respect to the
liability described below in this section; provided, however, that,
notwithstanding the foregoing provisions of this section, Borrower shall be
fully and personally liable and subject to legal action (a) for proceeds paid
under any insurance policies (or paid as a result of any other claim or cause of
action against any person or entity) by reason of damage, loss or destruction to
all or any portion of the Security Property, to the full extent of such proceeds
not previously delivered to Lender, but which, under the terms of the Loan
Documents, should have been delivered to Lender, (b) for proceeds or awards
resulting 

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from the condemnation or other taking in lieu of condemnation of all or any
portion of the Security Property, or any of them, to the full extent of such
proceeds or awards not previously delivered to Lender, but which, under the
terms of the Loan Documents, should have been delivered to Lender, (c) for all
tenant security deposits or other refundable deposits paid to or held by
Borrower or any other person or entity in connection with leases of all or any
portion of the Security Property which are not applied in accordance with the
terms of the applicable lease or other agreement, (d) for rent and other
payments received from tenants under leases of all or any portion of the
Security Property paid more than one month in advance, (e) for rents, issues,
profits and revenues of all or any portion of the Security Property received or
applicable to a period after any notice of default from Lender hereunder or
under the Loan Documents in the event of any default by Borrower hereunder or
thereunder which are not either applied to the ordinary and necessary expenses
of owning and operating the Security Property or paid to Lender, (f) for damage
to the Security Property as a result of the intentional misconduct or gross
negligence of Borrower or any of its principals, officers, managers, members or
general partners, or any agent or employee of any such persons, or any removal
of the Security Property in violation of the terms of the Loan Documents, to the
full extent of the losses or damages incurred by Lender on account of such
failure, (g) for failure to pay any valid taxes, assessments, mechanic's liens,
materialmen's liens or other liens which could create liens on any portion of
the Security Property which would be superior to the lien or security title of
the Security Instrument or the other Loan Documents, to the full extent of the
amount claimed by any such lien claimant, (h) for all obligations and
indemnities of Borrower under the Loan Documents relating to hazardous or toxic
substances or compliance with environmental laws and regulations to the full
extent of any losses or damages (including those resulting from diminution in
value of any Security Property) incurred by Lender as a result of the existence
of such hazardous or toxic substances or failure to comply with environmental
laws or regulations, and (i) for fraud or material misrepresentation by Borrower
or any of its principals, officers, managers, members or general partners, any
guarantor, any indemnitor or any agent, employee or other person authorized or
apparently authorized to make statements or representations on behalf of
Borrower, any principal, officer, manager, member or partner of Borrower, any
guarantor or any indemnitor, to the full extent of any losses, damages and
expenses of Lender on account thereof. References herein to particular sections
of the Loan Documents shall be deemed references to such sections as affected by
other provisions of the Loan Documents relating thereto. Nothing contained in
this section shall (i) be deemed to be a release or impairment of the
indebtedness evidenced by this Note or the other obligations of Borrower under
the Loan Documents or the lien of the Loan Documents upon the Security Property,
or (ii) preclude Lender from foreclosing under the Loan Documents in case of any
default or from enforcing any of the other rights of Lender except as stated in
this section, or (iii) limit or impair in any way whatsoever either the
Indemnity and Guaranty Agreement or the Hazardous Substances Indemnity Agreement
(collectively, the "Indemnity Agreement") of even date executed and delivered in
                    -------------------                                         
connection with the indebtedness evidenced by this Note or release, relieve,
reduce, waive or impair in any way whatsoever, any obligation of any party to
the Indemnity Agreement.

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                        ARTICLE II - GENERAL CONDITIONS
                        -------------------------------

     Section 2.1    No Waiver; Amendment.  No failure to accelerate the debt
                    --------------------                                    
evidenced hereby by reason of default hereunder, acceptance of a partial or past
due payment, or indulgences granted from time to time shall be construed (i) as
a novation of this Note or as a reinstatement of the indebtedness evidenced
hereby or as a waiver of such right of acceleration or of the right of Lender
thereafter to insist upon strict compliance with the terms of this Note, or (ii)
to prevent the exercise of such right of acceleration or any other right granted
hereunder or by any applicable laws; and Borrower hereby expressly waives the
benefit of any statute or rule of law or equity now provided, or which may
hereafter be provided, which would produce a result contrary to or in conflict
with the foregoing.  No extension of the time for the payment of this Note or
any installment due hereunder, made by agreement with any person now or
hereafter liable for the payment of this Note shall operate to release,
discharge, modify, change or affect the original liability of Borrower under
this Note, either in whole or in part unless Lender agrees otherwise in writing.
This Note may not be changed orally, but only by an agreement in writing signed
by the party against whom enforcement of any waiver, change, modification or
discharge is sought.

     Section 2.2    Waivers.  Presentment for payment, demand, protest and
                    -------                                               
notice of demand, protest and nonpayment, notice of intent to accelerate
maturity, notice of acceleration of maturity and all other notices are hereby
waived by Borrower.  Borrower hereby further waives and renounces, to the
fullest extent permitted by law, all rights to the benefits of any statute of
limitations and any moratorium, reinstatement, marshalling, forbearance,
valuation, stay, extension, redemption, appraisement, exemption and homestead
now or hereafter provided by the Constitution and laws of the United States of
America and of each state thereof, both as to itself and in and to all of its
property, real and personal, against the enforcement and collection of the
obligations evidenced by this Note or the other Loan Documents.

     Section 2.3    Limit of Validity.  The provisions of this Note and of all
                    -----------------                                         
agreements between Borrower and Lender, whether now  existing or hereafter
arising and whether written or oral, including, but not limited to, the Loan
Documents, are hereby expressly limited so that in no contingency or event
whatsoever, whether by reason of demand or acceleration of the maturity of this
Note or otherwise, shall the amount contracted for, charged, taken, reserved,
paid or agreed to be paid ("Interest") to Lender for the use, forbearance or
                            --------                                        
retention of the money loaned under this Note exceed the maximum amount
permissible under applicable law.  If, from any circumstance whatsoever
(including, without limitation, the receipt of any late charge or similar
amount), performance or fulfillment of any provision hereof or of any agreement
between Borrower and Lender shall, at the time performance or fulfillment of
such provision shall be due, exceed the limit for Interest prescribed by law or
otherwise transcend the limit of validity prescribed by applicable law, then
                                                                            
ipso facto the obligation to be performed or fulfilled shall be reduced to such
---- -----                                                                     
limit, and if, from any circumstance whatsoever, Lender shall ever receive
anything of value deemed Interest by applicable law in excess of the maximum
lawful amount, an amount equal to any excessive Interest shall be applied to the
reduction of the principal balance owing under this Note in the inverse order of
its maturity (whether or not then due) or at the option of Lender be paid over
to Borrower, and 

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not to the payment of Interest. All Interest (including any amounts or payments
judicially or otherwise under the law deemed to be Interest) contracted for,
charged, taken, reserved, paid or agreed to be paid to Lender shall, to the
extent permitted by applicable law, be amortized, prorated, allocated and spread
throughout the full term of this Note, including any extensions and renewals
hereof until payment in full of the principal balance of this Note so that the
Interest thereon for such full term will not exceed at any time the maximum
amount permitted by applicable law. To the extent that Lender is relying on
Article 5069-1.04, as amended, of the Revised Civil Statutes of Texas to
determine the maximum amount of Interest permitted by applicable law on the
principal of this Note, Lender will utilize the indicated (weekly) rate ceiling
from time to time in effect as provided in Article 5069-1.04, as amended. To the
extent United States federal law permits a greater amount of interest than is
permitted under Texas law, Lender will rely on United Stated federal law instead
of said Article 5069-1.04 for the purpose of determining the maximum amount
permitted by applicable law. Additionally, to the extent permitted by applicable
law now or hereafter in effect, Lender may, at its option and from time to time,
implement any other method of computing the maximum lawful rate under Article
5069-1.04, as amended, or under other applicable law by giving notice, if
required, to Borrower as provided by applicable law now or hereafter in effect.
In no event shall the provisions of Article 5069, ch. 15 of the Revised Civil
Statutes of Texas (which regulates certain revolving credit loan accounts and
revolving triparty accounts) apply to the indebtedness evidenced hereby. This
Section 2.3 will control all agreements between Borrower and Lender.
-----------

     Section 2.4    Use of Funds.  Borrower hereby warrants, represents and
                    ------------                                           
covenants that no funds disbursed hereunder shall be used for personal, family
or household purposes.

     Section 2.5    Unconditional Payment.  Borrower is and shall be obligated
                    ---------------------                                     
to pay principal, interest and any and all other amounts which become payable
hereunder or under the other Loan Documents absolutely and unconditionally and
without any abatement, postponement, diminution or deduction and without any
reduction for counterclaim or setoff.  In the event that at any time any payment
received by Lender hereunder shall be deemed by a court of competent
jurisdiction to have been a voidable preference or fraudulent conveyance under
any bankruptcy, insolvency or other debtor relief law, then the obligation to
make such payment shall survive any cancellation or satisfaction of this Note or
return thereof to Borrower and shall not be discharged or satisfied with any
prior payment thereof or cancellation of this Note, but shall remain a valid and
binding obligation enforceable in accordance with the terms and provisions
hereof, and such payment shall be immediately due and payable upon demand.

     Section 2.6    GOVERNING LAW.  THIS NOTE SHALL BE INTERPRETED, CONSTRUED
                    -------------                                            
AND ENFORCED ACCORDING TO THE LAWS OF THE STATE OF TEXAS.

     Section 2.7    Miscellaneous.  The terms and provisions hereof shall be
                    -------------                                           
binding upon and inure to the benefit of Borrower and Lender and their
respective heirs, executors, legal representatives, successors, successors-in-
title and assigns, whether by voluntary action of the parties or by operation of
law.  As used herein, the terms "Borrower" and "Lender" shall be deemed to
                                 --------       ------                    
include their respective heirs, executors, legal representatives, successors,
successors-in-title and 

                                                                   
PROMISSORY NOTE - Page 7                                                
<PAGE>
 
assigns, whether by voluntary action of the parties or by operation of law. If
Borrower consists of more than one person or entity, each shall be jointly and
severally liable to perform the obligations of Borrower under this Note. All
personal pronouns used herein, whether used in the masculine, feminine or neuter
gender, shall include all other genders; the singular shall include the plural
and vice versa. Titles of articles and sections are for convenience only and in
no way define, limit, amplify or describe the scope or intent of any provisions
hereof. Time is of the essence with respect to all provisions of this Note. This
Note and the other Loan Documents contain the entire agreements between the
parties hereto relating to the subject matter hereof and thereof and all prior
agreements relative hereto and thereto which are not contained herein or therein
are terminated.

Borrower's Tax Identification No.:  75-2726172

     IN WITNESS WHEREOF, Borrower has executed this Note as of the date first
written above.

                                        BORROWER:
                                        -------- 
                                        
                                        NEI REAL ESTATE, INC.,
                                        a Texas corporation
                                        
                                        
                                        By:
                                           -------------------------------------
                                              Name:  Barry B. Conrad
                                              Title: Chairman

                                                                                
PROMISSORY NOTE - Page 8