It's the deal one source called, "the industry's worst kept secret." But word is that Bethesda-based real estate investment trust American Capital (ACAS) is reportedly buying specialty servicer Residential Credit Solutions.

Both firms did not comment on the deal. As of today, RCS remains owned by Equifin Capital Partners.

The deal, if happening — and it is — would be part of a larger consolidation trend in the specialty servicer market. Many shops are likely to be bought up while others move into prime servicing, as more and more homeowners stay current on their mortgages.

The move makes sense for American Capital. The servicing of loans held in private-label mortgage backed securities is gaining interest, and a specialty servicer with ratings is often seen to have a leg up.

RCS is rated as a special servicer by both Standard & Poors and Fitch, and approved with HUD, Fannie Mae, and Freddie Mac.

American Capital, originates, underwrites and manages investments in middle market private equity. Real estate is only a portion of where it works. It also holds a presence in leveraged finance, energy & infrastructure and structured products.

American Capital manages $119 billion of total assets under management.