Nonprofit housing provider CASA has added seventy-nine apartments to its portfolio of affordable units in Durham, Wake, and Orange counties. (In case you haven’t heard, Durham is in need of affordable housing).

CASA announced Tuesday that it had purchased the forty-four-unit Underwood Apartments on Underwood Avenue in Durham and the thirty-five-unit Maplewood Apartments on West Chapel Hill Road in Durham, bringing its total stock to 490. The complexes were built by the same developer.

“This acquisition allows us to preserve the Underwood and Maplewood apartments as affordable rental housing in Durham and gives the current tenants assurance that their rent will remain affordable. These homes will continue to serve Durham renters with limited incomes for many more years to come,” CASA CEO Debra King said in a statement.

It’s the nonprofit’s largest acquisition in terms of units, says Missy Hatley, director of resource development for CASA. The sale closed Tuesday,

According to Hatley, the apartments will mostly be targeted at people earning 50 percent of the area median income or less, which is $25,700 for one person. Leases for current tenants will be honored, Hatley says, and deed restrictions ensure the units will remain affordable.

CASA tenants pay about 30 percent of their monthly income toward rent, with donations and housing vouchers helping to cover the rest. Hatley says some current tenants are already getting rental assistance through the federal Housing Choice Voucher program.

Thirteen of the units will be reserved for clients of Alliance Behavioral Health Care, which contributed to the $4 million purchase. It’s the first managed care organization in the state to contribute to the purchase of a property for people with disabilities, the statement says. Another eight units will be reserved for veterans.

North State Bank, BB&T, North Carolina Housing Finance Agency, Federal Home Loan Bank of Atlanta, and the city of Durham, which gave $240,000, also contributed.