Del Prete Brokerage Ltd., an eight-person Chicago sales management firm, has all the benefits of a well-equipped office, without the costly expenses of maintaining office space.

Besides retaining a telephone answering service and mailing address in a high-rent business district for less than $100 a month, the principals and sales staff use word processing equipment -- via telephone.

They simply call their word processing service in Chicago and dictate letters and reports to a tape recorder at any hour, day or night. The material is transcribed and returned to the callers within 24 hours. Any revisions can then be made by calling the service.

The word processing center, which charges $18 to $20 per hour, also manages Del Prete's records, such as accounts, sales, and commissions, and sends copies to the firm's partners.