Century 21 Real Estate Corp., the largest franchise network of independent brokers in the country, announced yesterday it intends to go public.

An initial offering of 700,000 shares of common stock, priced in the $11-13 range, will be made in early October. It is expected to be traded over the counter.

Headquartered in Irvine, Calif., Century 21 provides advertising, referral, training and escrow services to approximately 4,200 brokers in the United States and Canada. It does not actually sell real estate.

In return for the use of the name Century 21, the local realty compnay pays a purchase fee plus a percentage of gross sales. Franchises and services are sold through 32 regional organizations.

Century 21 owns eight of those organizations at present. Proceeds from the sale of 175,000 shares of company stock will be used to purchase more of these regional organizations. The other 575,000 shares are being offered by 10 major shareholders.

Chief among them is Century 21's chairman and president, Arthur E. Barlett, who founded the company in 1971. Prior to that, Barlett had his own real estate firm and a computer firm specializing in the transmission of real estate transactions to banks, appraisers, brokers, state and city agencies. Bartlett now owns 1.2 million shares of Century 21. The second largest stockholder is Marshall D. Fisher, a director, with 392,147 shares.

In the fiscal year ending in June, Century 21 listed assets of $7.2 million. Revenues for that year were $11.3 million. Profits totaled $1.9 million (83 cents a share).

Century 21, which came to Washington in August 1973, now has 61 broker franchises in the metropolitan area.

The offering will be made through a syndicate of underwriters, managed by Wedbush, Noble, Cooke, Inc. and Bateman Eichler, Hill Richards, Inc. of Los Angeles.

Franchised real estate chains have boomed in this country during the past decade altering the structure of an industry which once consisted almost entirely of small individual brokers working locally.

"The one-man office will always be there," said Bartlett. "The one who will find it difficult (to survive) is the office trying to maintain a sales staff of 10 and grow.We have to recognize that the biggest problem the independent broker faces is obtaining, training and retaining good sales people to serve the public."