Boston Community Capital has bought nearly 400 homes with troubled mortgages in the last four years; and it now has its sights set on Baltimore and Prince George's County in suburban Washington, D.C. -- two markets still navigating the fallout from the housing crash. The nonprofit organization purchases houses in some stage of foreclosure via its Stabilizing Urban Neighborhoods program. It then resells the residences to the occupants with new 30-year, fixed-rate mortgages. Company officials estimate that homeowners benefit from an average 40 percent reduction in their monthly mortgage payment and loan balance. With the help of a $25 million loan it received from East Boston Savings Bank earlier this year, Boston Community Capital is planning to acquire an additional 75 homes in Massachusetts and other states. At the same time, it is looking for local partners in Maryland to expand the initiative there.