The young man in the yellow rental truck surveyed the curving human line that wrapped around the Hampton Mall on Central Avenue in Capitol Heights yesterday morning and leaned out of his window to ask a question.

"Hey baby, what are people trying to get tickets to in there?"

Not tickets, he was told, just cheap money.

More than 200 people who would like to buy their first homes with the aid of a county program offering loan money at 10.9 percent interest began lining up Monday at 8 a.m. at the Prince George's County housing authority offices. By the time the doors opened at 10 a.m. yesterday to accept the first applications, the line of prospective homeowners equipped with lawn chairs, portable radios and blankets stretched past the supermarket, the drug store and on into the parking lot.

The man in the truck was not the only one to notice the scene's resemblance to a Capital Centre rock concert ticket line.

"Last week it was Prince," said Charles Fletcher, referring to the popular rock star who will be at the Capital Centre next month. "This week it's 10.9."

Fletcher and his wife Margaret, who arrived at the Hampton Mall on Tuesday, said they have figured a low-interest loan will save them at least $170 a month in mortgage payments on a $76,000 town house they have contracted to purchase in Upper Marlboro.

The mortgage program, funneled through the state from the federal government, is intended to help middle-income persons afford their first home. It offers interest rates roughly 3 percentage points below the current market rate, which housing officials said averages about 14 percent. County officials said that $37 million in loans for new and existing housing will be made to about 500 applicants in this round.

Last year, in Prince George's first crack at the program, $28 million in loans were made to about 350 people, officials said.

The Reagan administration suspended the program for the first six months of this year, arguing that because the bonds that pay for the mortgage money are exempt from federal and state taxes, governments are losing millions a year in revenues.

But Bernard Tetreault, executive director of the Montgomery County Housing Opportunities Commission and president of the Association of Local Housing Finance Agencies, argues that the boon such programs provide to the housing industry and to individual homeowners more than offsets its cost.

"As interest rates go up, say, from 10 to 11 percent, that's about two million more people who can't afford to purchase a home," he said. "By making a differential in the interest rate like this, you free up three or four million people who can now afford to buy."

The National Association of Realtors reported last month that the high level of mortgage interest rates "clearly is damaging the housing affordability picture for thousands of families throughout the nation." That, too, is the case in Prince George's County, said Major Riddick, who is director of the county's housing authority.

The state of Maryland, the City of Baltimore and Montgomery and Washington counties have sponsored similar programs that offer mortgage money at discount interest rates.

In the District, housing officials said $30 million in low-interest mortgage money made available in August has found few takers to date. The District program offers 30-year mortgages at 11.4 percent.

The state of Maryland, meanwhile, will offer $108.9 million in loans at 10.4 percent interest beginning Oct. 16. Because Montgomery and Prince George's counties run their own programs, residents from those jurisdictions are not eligible for the state's mortgage loans.

Prince George's housing officials said 216 people had applied yesterday for mortgage money to purchase existing houses. The money was available on a first-come, first-served basis. Other loans that have been earmarked for new construction will be made through approved lenders for approved developments, county officials said.

Bill and Gwen Philpott of Riverdale, who have two young sons, said the low-interest loan will allow them to purchase a $71,000 rambler they have a contract on in New Carrollton. "It's worth it for us to wait in line," Gwen Philpott said. "We couldn't afford $1,000-a-month mortgage payments."