<PAGE>
 
                                                                   EXHIBIT 10(N)

                         [LOGO OF ICIFC APPEARS HERE]
                            ICI FUNDING CORPORATION
                            -----------------------
            A SUBSIDIARY OF IMPERIAL CREDIT MORTGAGE HOLDINGS. INC.

                                                          Commitment No. MA3660
                                                           Seller No. 000600013

September 4, 1997


Mr. Russ Kidder
Managing Director
EMB MORTGAGE CORPORATION
575 Anton Blvd., Suite 200
Costa Mesa, CA 92626

RE:  MASTER COMMITMENT TO PURCHASE JUMBO AND CONFORMING RESIDENTIAL MORTGAGES

Dear Mr. Kidder:

ICI FUNDING CORPORATION, a subsidiary of IMPERIAL CREDIT MORTGAGE HOLDINGS,
INC., hereinafter referred to as "Buyer", hereby commits to purchase/fund from
EMB MORTGAGE CORPORATION, hereinafter referred to as "Seller" first trust deed
mortgage loan(s) pursuant to the terms and conditions set forth herein and the
ICIFC Sellers Guide, the PROGRESSIVE SERIES I - VI AND PROGRESSIVE EXPRESS Guide
(Guides) as amended from time to time, and the ICIFC Sale Agreement. Seller is
bound by all conditions of the Guides and Sale Agreement or under a separate
written agreement. By executing this Commitment, Buyer hereby agrees to
purchase, and Seller hereby agrees to sell those certain Loan(s), subject to
terms and conditions of this Commitment.

     1.   AMOUNT OF COMMITMENT:  Buyer will offer Seller $75,000,000 commitment
          --------------------    
          in exchange for 45,000 shares of Seller's non restricted stock at a
          price of $2.00.

     2.   TERM OF COMMITMENT: This is a six month (6), optional delivery, Master
          ------------------                                                    
          Commitment. The Commitment expiration date will be March 15, 1998 or
          upon the fulfillment of the amount of commitment, whichever occurs
          first. All loans must be committed and delivered to Buyer in
          purchasable form prior to expiration of this Commitment.

     3.   COMMITMENT FEE: An up front commitment fee of one-eighth of one
          --------------                                                 
          percent (.125%) will be waived by Buyer in exchange for 45,000 shares
          of Seller's non restricted stock at a price of $2.00 (assuming the
          stock currently trades at $4.00). $1,050 IN UNPAID PRIOR UNDERWRITING
          FEE IS PAYABLE TO BUYER UPON THE EXECUTION OF THIS COMMITMENT.
<PAGE>
 
     4.   ELIGIBLE PRODUCT TYPES: Seller may sell and Buyer will purchase 
          ----------------------        
          mortgage products pursuant to the terms of the Guide(s), the following
          types of mortgage loans:

          .    Progressive Series I - VI loan programs;
          .    Progressive Express programs, Retail originations.

          FOR THIRD PARTY ORIGINATION EXPRESS PROGRAM, SELLER MUST MEET THE
          FOLLOWING CRITERIA PRIOR TO SUBMITTING LOANS FOR PURCHASE:

          .    PROVIDE SAMPLE BROKER APPROVAL PROCESS PACKAGE TO ICIFC V.P.
               SELLER ADMINISTRATION FOR APPROVAL OF PROCEDURES. 
          .    MANDATORY ON-SITE TRAINING (COMPLETED 6/26/97).

          SELLER MUST MAINTAIN THE FOLLOWING FOR CONTINUOUS IN TPO EXPRESS
          DELIVERY:

          .    SELLER MUST BE A CURRENT MINIMUM CLASS II DELEGATION LEVEL.
          .    SELLER TO PROVIDE MINIMUM 10% QUARTERLY Q.C. RESULTS TO ICIFC.

          Each product offers the following type of mortgage loan:

          .    30 year fully amortizing fixed rate;
          .    15 year fully amortizing fixed rate;
          .    6 month LIBOR semi-annually adjusting ARMs with 1/6 Caps;
          .    2 year fixed Rollover to 6 month LIBOR semi-annually adjusting
               ARMs;
               
     5.   UNDERWRITING GUIDELINES: Except as set forth herein, including the 
          -----------------------  
          attached conditions, loan documentation and underwriting must be in
          compliance with the Guide(s). Any exception to the guidelines not
          specified within this commitment, must be approved by Buyer prior to
          the delivery of the loan for purchase. Program parameters and pricing
          parameters are subject to change.

     6.   PRIOR UNDERWRITING APPROVAL BY BUYER: Seller may submit loans to Buyer
          ------------------------------------       
          for prior approval. Loans that are rejected by Buyer are ineligible
          for purchase. If a loan has been rejected by another conduit, Seller
          must notify Buyer of reason for rejection at the time of loan
          submission. Prior underwriting is required by Buyer on loan as
          parameters stated in the attached Exhibit "B".

          Regardless of the underwriting delegation given herein as shown in
          Exhibit B, Buyer will require prior underwriting for the following:
          .    Any loans with exceptions to the Guideline(s);
          .    Cash reserves less than required by Guideline(s);
          .    Non-arms length transactions (as define in ICIFC's Underwriting
               Guideline);
          .    Credit history and delinquent credit outside of program
               guidelines;
          .    2 years employment not in the same line of work;
<PAGE>
 
     7.   DELEGATED UNDERWRITING: Seller is delegated as per attached Exhibit B.
          ----------------------        
          All loans not delegated as per attached must be prior approved by
          Buyer. Buyer will have the right to terminate all or any portion of
          the delegation given to the Seller providing Buyer notify Seller in
          writing stating a termination date of such delegation.

     8.   PRIOR APPROVAL BY CONTRACT SERVICES: Seller may select prior 
          -----------------------------------    
          underwriting by Contract Service Underwriting (acceptable to Buyer)
          for Progressive Series (Select) and Progressive Express as stated in
          Exhibit B. Loans rejected by another conduit or Buyer will not be
          eligible for Contract Service Underwriting.

          Acceptable Mortgage Insurance Contract Services:
          .    CMAC
          .    UGI
          .    PMI
          .    GE
          .    RMIC

          Unacceptable Mortgage Insurance Contract Services:

          .    MGIC

     9.   PURCHASE PRICE: The purchase price will be based on the posted rates 
          --------------         
          and prices, plus any pricing adjustments on Knight Ridder screens 7271
          through 7289 for the applicable loan program being locked in. For the
          following loan programs, the screen price will be increased at time of
          rate lock in:

          .    FIXED RATE PROGRESSIVE SERIES I - III AND PROGRESSIVE EXPRESS 
               LOANS - ONE-HALF OF ONE PERCENT (.50%);
          .    FIXED RATE PROGRESSIVE SERIES III+ - VI LOANS - FIVE-EIGHTHS OF
               ONE PERCENT (.625%);
          .    TWO-YEAR ARM LOANS - ONE-EIGHTH OF ONE PERCENT (.125%); (ALL
               PROGRAMS)
          .    SIX-MONTH ARM LOANS - FIVE-EIGHTHS OF ONE PERCENT (.625%); (ALL
               PROGRAMS)

     9a.  PRICING INCENTIVE: BUYER AGREES TO PAY AN ADDITIONAL 5 BASIS POINT 
          -----------------         
          REBATE FOR LOANS LOCKED ON THE INTERNET, THROUGH DECEMBER 31ST, TO
          QUALIFIED CUSTOMERS; LOANS MUST BE CLOSED WITHIN COMMITMENT PERIOD TO
          QUALIFY FOR THIS BONUS.

     9b.  60%LTV OR LESS PRICING ENHANCEMENT: FOR ALL PROGRAMS, LOANS LOCKED AND
          ----------------------------------     
          PURCHASED WITH LTVS OF 60% OR LESS, THE POSTED PRICE WILL BE INCREASED
          BY 50 BASIS POINTS; THIS REBATE IS IN ADDITION TO ANY OTHER PRICING
          INCENTIVES.

     10.  LOCK-IN PROCEDURES: Seller will reference this Master Commitment 
          ------------------    
          number and specify the preferred pricing parameters at time of
          commitment, and follow the standard Guide requirements for best
          efforts lock-in. Bulk lock-ins are allowed for a
<PAGE>
 
          minimum of $500,000 and are considered mandatory delivery, plus or
          minus two percent (2%).

     11.  PRIVATE MORTGAGE INSURANCE: All Progressive loans with balances 
          -------------------------- 
          exceeding the lesser of 80.01% of the purchase price or the appraised
          value shall be insured by a mortgage insurance company acceptable to
          Buyer. Said mortgage insurance coverage shall be in a form acceptable
          to Buyer and must reduce exposure to at least seventy-five (75%)
          percent of the original value on Progressive product. For loans
          originated under Progressive Express, refer to Underwriting Guidelines
          attached for specific mortgage coverage and companies.

     12.  DELIVERY RESTRICTIONS: Property types and program percentages are
          ---------------------                                            
          unrestricted except for the PROGRESSIVE program which will be subject
          to delivery limitations set forth below:

                       DELIVERY PERCENTAGE LIMITATIONS:
                       ------------------------------- 

          o    LTV LIMITATIONS: Allow a maximum of 30% of the aggregate amount
               of all Progressive delivered to exceed 80%LTV to a maximum of
               95%LTV, with mortgages greater than 90% LTV not to exceed 20% of
               the Commitment amount;
          o    REDUCED DOC: Not to exceed 40% of the aggregate amount of all
               Progressive delivered;
          o    NOO and SECOND HOME: Not to exceed 15% of the aggregate amount of
               all Progressive delivered;
          o    LOANS GREATER THAN $650,000: Not to exceed 20% of the aggregate
               amount of all Progressive delivered;
          o    2-4 UNIT PROPERTIES: Not to exceed 5% of the aggregate amount of
               all Progressive delivered.
          o    NO INCOME/NO ASSET: Not to exceed 20% of the Commitment amount;
          o    80% NO RATIO: Not to exceed 15% of the commitment amount;
          o    100% FINANCING: Not to exceed 5% of the Commitment amount;
          O    PROGRESSIVE EXPRESS: NOT EXCEED 50% OF THE TOTAL COMMITMENT
               AMOUNT; 
          O    PROGRESSIVE EXPRESS GEOGRAPHIC LIMITATION: NOT MORE THAN 40% OF
               THIS COMMITMENT MAY CONSIST OF LOANS LOCATED IN CALIFORNIA.

     13.  SERVICING: Loans shall be sold in their entirety to Buyer, with 
          ---------        
          servicing rights of such loans released to Buyer upon purchase. All
          servicing rights of loans purchased according to this Commitment shall
          be included with this purchase and shall be considered transferred and
          owned by Buyer as of the date of funding of each loan purchase and
          Seller shall have no further rights or claims of any type as of the
          date of each loan purchase.

<PAGE>
 
          All servicing activities, records, funds and including, but not
          limited to, any escrow and buydown balances, all funds held for the
          benefit of these loans, and insurance records shall be transferred to
          Buyer on the date of purchase. The cost for establishing new tax
          service contracts will be at Seller's expense.

     14.  PAIR-OFF: Once loans are locked in for block commitments, a pair-off 
          --------     
          fee of one eighth of one percent (.125%), plus any market movement,
          will be assessed on the difference, if any, between the Commitment
          amount (minus delivery tolerance) and the actual amount delivered.
          Seller will remit payment to Buyer for the amount of the pair-off fee
          within ten (10) days from the expiration date of the commitment.

     15.  SALES AND FUNDING: Funding will occur within seventy two (72) hours of
          -----------------                                                     
          delivery, provided Seller delivers all required documents and
          outstanding conditions, in addition to, the original promissory notes
          evidencing the loans to be purchased, duly endorsed in favor of Buyer,
          prior to the purchase date. Seller shall furnish copies of the
          assignment of deed of trust or mortgage, in addition to other
          documents outlined in the Guide.

          In addition to any applicable pricing adjustments posted on applicable
          Knight Ridder screens the following additional fees will be charged on
          all loans purchased by Buyer:

<TABLE> 
               <S>                       <C> 
               Tax Service Fee -         $59.00 or prevailing TransAmerica rate;
               Administrative Fee -      $125.00 per loan;
               Prior Underwriting Fee -  $75.00 per loan;
</TABLE> 

     16.  GEOGRAPHICAL RESTRICTIONS: Unless otherwise stated, mortgages secured 
          -------------------------          
          by properties located in the continental United States and Hawaii are
          eligible for purchase. Properties located in the state of Alabama and
          Alaska are not eligible for purchase.

     17.  WARRANTIES AND REPRESENTATIONS: Seller, to induce Buyer to fund loans,
          ------------------------------                                        
          warrants, represents and covenants to Buyer that in connection with
          each loan transaction:

          Warranties within this agreement shall survive the transfer to and
          purchase by Buyer and shall be deemed to successors and assigns. No
          waiver of any default or breach by Seller shall be implied from any
          omission by Buyer or its assigns to take any action on account of such
          default if such default continues or is repeated. No written waiver
          shall affect any breach other than the breach specified in such waiver
          and only to the extent therein expressly stated. Any failure or delay
          by Buyer or its assigns in exercising any rights, power, or remedy
          hereunder shall not be deemed a waiver thereof.
<PAGE>
 
     17a. PROGRESSIVE EXPRESS SELLER'S CERTIFICATION: Seller makes the following
          ------------------------------------------                            
          certification to induce Buyer to commit to the purchase of Progressive
          Express loans.

          o    The loan terms furnished in Progressive Express Application are
               true, accurate, and complete.
          o    The information contained in Progressive Express Application was
               obtained directly from the borrower by a full-time employee of
               Seller or its duly authorized agent.
          o    The credit report submitted on the subject borrower, co-borrower,
               if applicable, was ordered by Seller or its duly authorized agent
               directly from the credit bureau which prepared the report was
               received directly from said credit bureau.

     18.  INDEMNIFICATION: Without limiting any of Buyer's rights contained in 
          ---------------       
          this agreement, Seller shall indemnify, defend and hold Buyer, its
          successors and assigns, and its officers, agents, and employees
          harmless including judgments, court costs, and actual credit reporting
          agency costs, and attorney fees related to any breach of Seller
          warranty, representation, or covenant contained in this agreement.
          This indemnification shall survive the terms of this agreement for all
          loans closed until the sooner of: (a) written release by Buyer and any
          successor or assign: (b) payoff of the loan; or (c) the lapse of any
          applicable statute of limitation.

     19.  MODIFICATION, WAIVER OR AMENDMENT: No modification or waiver of or
          ---------------------------------                                 
          amendment to any of the terms of this Commitment shall be effective
          unless it is in writing signed by all parties hereto.

     20.  ASSIGNMENT: This Commitment is only assignable by Buyer. This 
          ----------      
          Commitment is not intended to benefit any third party. Buyer may only
          assign this Commitment to a party who has the ability to perform all
          of Buyer's obligations under this Commitment.

     21.  APPLICABLE LAW: The Commitment shall be governed by and construed 
          --------------       
          under the laws of the State of California, to the jurisdiction of
          whose courts the parties hereby agree to submit.

     22.  ENFORCEMENT: In the event of any action by Buyer or Seller to enforce 
          -----------    
          this Commitment, the prevailing party shall be entitled to receive, in
          addition to all other relief, the costs thereof including, without
          limitation, attorneys fees and court costs.

     23.  ENTIRE AGREEMENT: This Commitment and any agreement, document or 
          ----------------        
          instrument attached hereto or referenced herein integrates all of the
          terms and conditions mentioned herein or incidental hereto, and
          supersedes all oral negotiations and prior writings regarding the
          subject matter hereof.
<PAGE>
 
     24.  NOTICES: Buyer and Seller mutually agree that each of them will 
          ------- 
          immediately upon demand by the other party, execute such documents or
          perform such acts as may be required by such party to perform their
          objectives under this agreement; and refusal to cooperate and execute
          documents or perform acts required by this agreement shall be
          considered a material breach hereof and shall suspend the performance
          of non-breaching party frill and complete performance of the breaching
          party.

          All notices, requests, demands or other communications that are to be
          given under this contract shall be in writing, addressed to the
          appropriate parties and sent postage prepaid to the address below:

                    If to Buyer:   ICI Funding Corporation
                                   20371 Irvine Ave., Bldg. A
                                   Santa Ana Heights, CA 92707
                                   ATTN: Mary Glass

                    If to Seller:  EMB MORTGAGE CORPORATION
                                   575 Anton Blvd., Suite 200
                                   Costa Mesa, CA 92626
                                   ATTN: Russ Kidder

     25.  SEVERABILITY: Whenever possible, each provision of this Commitment 
          ------------           
          shall be interpreted in such manner as to be valid and effective under
          applicable law, but if any such provision shall be ineffective to the
          extent of such prohibition or invalidity without invalidating the
          remainder of such provision or the remaining provisions of the
          Commitment.

     26.  HEADINGS: The headings used herein are used for convenience only, are 
          --------          
          not part hereof and shall not be used in construing this Commitment.

     27.  COUNTERPARTS: This Commitment may be executed in any number of 
          ------------     
          counterparts and all such counterparts taken together shall be deemed
          to constitute on and the same instrument.

     28.  FINANCIAL CONDITION: Prior to, or concurrent with the execution of 
          -------------------     
          this Commitment, Seller agrees to submit a recent audited financial
          statement. Unless otherwise waived by Buyer, Seller must have a
          minimum audited net worth of at least $1,000,000 in order to deliver
          loans under this Commitment.
<PAGE>
 
If the terms and conditions of the Commitment are acceptable to Seller, please
execute the acceptance where indicated on this Commitment and return one copy of
the signed agreement A signed copy hereof signed by Seller must be received by
Buyer or its authorized representative within five (5) business days of receipt
by Seller, or this agreement will be considered null and void.

The individuals executing this Commitment by their signatures do hereby certify
they are duly authorized to execute this document on behalf of the parties they
represent.

     /s/ Mary C. Glass-Schannault
     ------------------------------------------
     By:  Mary C. Glass-Schannault
          Senior Vice President
          ICI FUNDING CORPORATION

     /s/ James W. Dickinson 
     ------------------------------------------
     By:  James W. Dickinson 
          Vice President
          ICI FUNDING CORPORATION


We hereby acknowledge and accept all of the terms and conditions of this
Commitment for the sale of the Loans described herein:


     Date:  9-12-97 
          --------------------------


     /s/ Russ Kidder
     ------------------------------------------
     By:  Russ Kidder
          Managing Director
          EMB MORTGAGE CORPORATION