It wasn't very long ago that Wall Street heavies like the Blackstone Group (NYSE:BX) and new market entries like B. Wayne Hughes' American Homes 4 Rent (NYSE:AMH) were lapping up thousands of single-family foreclosures across the country each month, rehabilitating them and renting them out – sometimes to the previous owners.

Blackstone spent $2.5 billion in 2012 to purchase 16,000 such homes, swelling its portfolio of rentals to approximately 200,000 properties, while newcomer American Homes holds 21,000. It seemed that there was no slowdown in sight, and two brand new real estate investment trusts were born early last year to take advantage of this nascent market: Silver Bay Realty (NYSE:SBY) and Altisource Residential (NYSE:RESI).

A previously hot market is experiencing a chill
By the end of 2013, however, the foreclosure-to-rental model began to stall. In the formerly fertile Tampa Bay, Florida market, Blackstone's Invitation Homes, Silver Bay, and American Homes 4 Rent all decreased spending by 50% over a six-month period from spring to fall.

Now, the rental payment bond sales that grew out of the foreclosure-purchasing business – the proceeds of which helped to fund new spending sprees – are losing traction, too. The keen interest that greeted Blackstone's first securitization offering last November seems to have waned, even as American Homes works with Goldman Sachs to launch its own rental payment bond. Just this past December, analysts at Credit Suisse opined that the rental securitization market could hit $5 billion this year.

That prediction may not pan out. Since October, rents backing Blackstone's November offering dropped by 7.6% between October and January, as more vacant properties failed to carry their weight.

A new era?
It seems that the single-family business model may be wearing itself out. Fewer foreclosures on the market, along with rising house prices, have held back the previously feverish pace of growth. Faced with fewer brick-and-mortar prospects, institutional investors are now purchasing the nonperforming loans that back the 2.2 million home loans that are either delinquent or actually in foreclosure.

Buying batches of NPLs from banks and the federal government is a market that could reach $40 billion in 2014 , and allows these companies access to distressed properties at a discount of 65% to 80% of property values. Big players in this area are American Homes and Altisource Residential, while Blackstone has announced that it has no plans to join in.

Is this business model beginning to wind down? It certainly looks like that might be the case. Of course, the idea was somewhat self-limiting to start with; the ultimate irony is that the industry itself is likely a big part of the cause of its own demise. For its part, Silver Bay doesn't seem overly concerned with a lack of available properties – it recently announced that it has increased its borrowing capacity to $350 million from $200 million in order to take advantage of what it sees as still-favorable market conditions.

None of the companies seem to be selling the homes in their portfolios, so the rental part of the model still seems intact, at least for the time being. As the opportunities to add to the empires of these companies dwindle, however, it may eventually come down to these entities buying each other – rather than foreclosed-upon single-family abodes.

Tried-and-true stock picks
As every savvy investor knows, Warren Buffett didn't make billions by betting on half-baked stocks. He isolated his best few ideas, bet big, and rode them to riches, hardly ever selling. You deserve the same. That's why our CEO, legendary investor Tom Gardner, has permitted us to reveal The Motley Fool's 3 Stocks to Own Forever. These picks are free today! Just click here now to uncover the three companies we love. 

Amanda Alix has no position in any stocks mentioned. The Motley Fool recommends Goldman Sachs. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.