<PAGE>

                                                                    EXHIBIT 10.7

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

                                                                 LOAN NO. 240738
$1,090,000.00                        Dated to be effective as of October 8, 1997


Dallas, Texas

     FOR VALUE RECEIVED, the undersigned, NEI 4647, INC., a Texas corporation
                                                                             
("Borrower"), whose address is 4647 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 NINETY THOUSAND AND NO/100 DOLLARS ($1,090,000.00),
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
                        --------------------------------

     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 $8,550.45 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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PROMISSORY NOTE - Page 1                                               Initials
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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.

     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 Real Estate, Inc. in the amount of $1,610,000.00 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 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


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PROMISSORY NOTE - Page 2                                               Initials
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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.
                                             -----------       

     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.

     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 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


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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.

     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 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,


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(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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PROMISSORY NOTE - Page 5                                               Initials
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                        ARTICLE II - GENERAL CONDITIONS
                        -------------------------------

     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.

     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.

     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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PROMISSORY NOTE - Page 6                                               Initials
<PAGE>
 
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.
-----------

     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.

     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.

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

     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 assigns, whether by voluntary action of the parties or by operation of
law.  If Borrower consists of more than one
<PAGE>
 
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.:  75-2726835

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

                                                BORROWER:
                                                -------- 

                                                NEI 4647, INC.,
                                                a Texas corporation


                                                By:
                                                   --------------------------
                                                   Name:  Barry B. Conrad
                                                   Title: Chairman


PROMISSORY NOTE - Page 8