Montgomery County will provide $3 million this year to stimulate construction of new rental housing and provide rent supplements for low-income families under a program announced yesterday by County Executive Charles W. Gilchrist.

The county plans to invest the money and use the interest it earns to provide rent supplements for moderate-income tenants in newly constructed housing.

In addition, the county will make a $1 million rehabilitation loan to the developers of the 33-year-old University Manor Apartments in Silver Spring, where at least 20 percent of the 136 units will be reserved for moderate-income tenants.

After the University Manor units have been renovated, 50 low- and moderate-income tenants will be eligible for federal rent subsidies. Those tenants live in the complex now and will be unable to pay the higher rents charged after renovation is complete.

Since 1977, nearly 6,000 apartments in the county have been converted to condominiums, Gilchrist said. There are now approximately 55,000 rental units in the county, and 6,000 low- and moderate-income families on a waiting list for housing.

The Montgomery County Council unanimously passed a measure yesterday designed to help minority-owned companies get more county contracts.

Previously, firms had to enter a complicated bidding process for any county contract worth more than $3,000. Under the new measure, companies will not have to enter the process for contracts worth $7,000 or less. The bill is designed to help firms that are not financially powerful enough to compete with larger companies in the formal bidding process.

Beginning July 1, it will cost more to get married in Montgomery County. The County Council yesterday raised the price of a marriage license from $5 to $10. The extra money will be used to augment the $990,000 budget for the county's badly understaffed Community Crisis and battered women's shelter