Fairfax County’s Board of Supervisors agreed Tuesday to back a $4.8 million loan for a Northern Virginia nonprofit to acquire and rehabilitate a 184-unit apartment complex as affordable housing in the Alexandria area of the county.

Wesley Housing Development Corp. has moved to acquire the Mount Vernon Apartments on Russell Road in the county’s Lee District for $20.7 million.

To make the deal feasible, the nonprofit asked the county for a loan through its Housing Blueprint program that would bolster its chances for obtaining tax credits for the project from the Virginia Housing and Development Authority.

Affordable housing became a key issue of contrast between Republicans and Democrats during last fall’s election, with some GOP candidates arguing that the county has been subsidizing “luxury.”

But the board voted unanimously to back the deal, and Supervisor Patrick S. Herrity (R-Springfield) took pains Tuesday to say that the Mount Vernon Apartments deal was exactly what the county should be doing.

“There’s a lot to like in this,” Herrity said, especially that the units will be owned and managed by the nonprofit, not the county. “It’s also going to the truly low-income and disabled.”

Supervisor Jeffrey C. McKay (D-Lee) agreed.

“I think this is the type of project that matches exactly the intent of our Housing Blueprint,” McKay said.

The recession has forced the county to pull back on affordable housing initiatives and refocus its efforts on its neediest residents. From fiscal 2006-09, the county set aside funds equal to one cent of its real estate tax rate to subsidize affordable housing, but then cut that sum in half to balance the budget in fiscal 2010. From fiscal 2006-11, the county amassed almost $105 million to preserve affordable housing; the fund provided nearly $15 million in the current fiscal year.

The Mount Vernon Apartments is a complex with one- , two- and three-bedroom garden-style rentals on 7.73 acres. Wesley Housing, which has been in business for more than 30 years, manages 875 units in 15 properties.

Under the terms described by county staff, Wesley would purchase the 47-year-old Mount Vernon Apartments from Russell Road LP, which would make a charitable contribution of $1.4 million toward the transaction. The 184 units would serve households at or below 30 percent, 50 percent and 60 percent of area median income. The average median income, which is set by HUD, is $107,500 for a family of four, $96,750 for a family of three, $86,000 for two, and $75,250 for a single person. Nineteen units would be available for people with disabilities.

A previous bid by Wesley Housing to buy the property fell through when the nonprofit failed to line up the tax credits with the VHDA.