The Ryland Group Inc. DESCRIPTION: A home-building company involved in the construction and sale of detached and attached homes. The company has a wholly owned subsidiary, Ryland Mortgage Co., which provides financing for Ryland customers. FOUNDED: 1967. TOP EXECUTIVES: James Ryan, chairman; James F. McEneaney, president.

Ryland is building homes or has built homes in Philadelphia, Baltimore, Washington, Richmond, Raleigh, Orlando, Cincinnati, Columbus, Dayton, Indianapolis, Dallas and Houston. With the help of prefabricated wall panels and other building components, the company is constructing houses in an average of 73 days. Last year, Ryland Group opened a panelized plant in Houston, which supports three out of four housing areas, manufacturing components for use on homes.

The Columbia-based home builder posted earnings results common to the building industry this year: $3.02 million (99 cents a share), compared with earnings of $6.57 million ($2.12) from a year before. Sales were $230.88 million, down 18 percent from $258.04 million the prior year.

Rouse Co. DESCRIPTION: A Columbia real estate and development firm with subsidiaries engaged in investment and mortgage banking services; 53 retail shopping centers (OTC). FOUNDED: 1939. TOP EXECUTIVES: James W. Rouse, chairman; Mathias J. DeVito, president and CEO.

Rouse, the company that operates 53 chrome and glass and glittering shopping centers across the country and has a division to build "new towns," is a name that's becoming synonymous with the renovation of dying downtowns. City leaders see the economic and social effects of Rouse projects in Boston and Baltimore, then give the company a call to see what it can do for their communities. During 1981, Rouse completed five major retail development projects, including White Marsh Mall in Baltimore County and expansion of The Mall in Columbia.

Rouse officials call the company's outlook excellent, although for the building industry at large, the picture is "uncertain, even scary." On Rouse's to-do list for 1982-85 are at least 12 major projects, including Painters Mill and Area 5 in Baltimore and National Center in downtown D.C.

B. F. Saul Investment Trust DESCRIPTION: The trust's principal businesses are ownership and development of income-producing properties and the conversion of apartment projects into condominiums (NYSE). FOUNDED: 1964. TOP EXECUTIVE: B. Francis Saul II, chairman.

In fiscal year 1981, the trust sold a total of 669 condominium units. The effect of rising interest rates, however, was to produce a steady decline in sales, from 342 units sold in the first quarter to 71 units in the last quarter. In the first quarter of this year, the company sustained a loss of $46,000, compared witho what it called "an unusually large profit" during the first quarter of last year, when it sold 342 condominium units at a $7.2 million profit.

Chairman Saul said this January that the biggest hurdle his company was going to encounter in 1982 would be to find long-term financing for projects already planned. Since that time, the company has not been able to obtain satisfactory financing for a major, 368,000-square-foot project in Atlanta. At the same time, the company has leased about 40 percent of the space in the first in a series of high-rise towers in an Atlanta office park. Leasing of space in the firm's other major project, located in Gaithersburg, is reported to be progressing, and construction is expected to be completed sometime in June. In addition, the company will spend about $5 million this year for "replacements and renovations" at its existing, income-producing properties.

National Corporation for Housing Partnerships DESCRIPTION: Created by Congresss, it is the largest producer of housing for families of low and moderate income in the nation, operating in 42 states, the District of Columbia and Puerto Rico. FOUNDED: 1970. TOP EXECUTIVES: George W. DeFranceaux, chairman; George M. Brady Jr., president and chief executive officer.

The privately funded organization, operating on a charter from the federal government, reported last year it has become the "largest private producer of low and moderate-income rental housing" over the past 12 years. Last year the company added two new states, Hawaii and Kentucky, to its area of operation, but overall production of housing units declined because of high interset rates. With the new administration in the White House, NCHP plans to change its operations and focus on new activities, including the acquisition and syndication of existing government-assisted and conventionally financed rental developments.