Renting is on the ascendancy over homeownership, says real estate attorney Shari Olefson, author of "Financial Fresh Start."

One reason why was the expiration of the Mortgage Debt Forgiveness Relief Act at the end of last year, she tells Yahoo. That law allowed homeowners to forgo paying taxes on money that banks forgave in their underwater mortgages.

So now some homeowners will go into foreclosure instead of making a short sale, Olefson says. Foreclosures will occur most often in places still on the mend from the housing crash, she says.

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"These also happen to be the states where you've got the big companies, the Blackstones and the big funds, investing in rentals. So a lot of these properties will end up as rentals."

The big investors also are driving home prices higher, forcing more people to rent, Olefson says.

"Prices of homes in an area should be based on the area's income, but investors are bidding based on the rent they think they can generate," she said.

"So the homes are becoming less affordable for folks who want to buy, making renting just a much more viable option."

Meanwhile, Wall Street now is beginning to securitize the mortgages on these rental homes.

This securitization market has the potential to total as much as $1.5 trillion, according to a recent Wall Street estimate, The New York Times reports.

"The investment and lending opportunities are immense and perhaps just beginning," Jade Rahmani, a real estate analyst with Keefe, Bruyette & Woods, writes in a report obtained by the paper.

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