Arlington lost 13,500 total affordable housing units between 2000 and 2013. MARKs are market affordable units. MARKs are units that are not regulated by the County or other public agencies. CAFs are committed affordable housing units are either wholly owned by nonprofits, are guaranteed by agreement with the federal, state, or county government to remain affordable to low and moderate income households, or units that receive a government subsidy to assist with the property’s purchase.