RIVERSIDE, Calif. — At least 20 times a day, Alan Hladik walks into a fixer-upper and tries to figure out if it is worth buying.

As an inspector for the Waypoint Real Estate Group, Mr. Hladik takes about 20 minutes to walk through each home, noting worn kitchen cabinets or missing roof tiles. The blistering pace is necessary to keep up with Waypoint’s appetite: the company, which has bought about 1,200 homes since 2008 — and is now buying five to seven a day — is an early entrant in a business that some deep-pocketed investors are betting is poised to explode.

With home prices down more than a third from their peak and the market swamped with foreclosures, large investors are salivating at the opportunity to buy perhaps thousands of homes at deep discounts and fill them with tenants. Nobody has ever tried this on such a large scale, and critics worry these new investors could face big challenges managing large portfolios of dispersed rental houses. Typically, landlords tend to be individuals or small firms that own just a handful of homes.

But the new investors believe the rental income can deliver returns well above those offered by Treasury securities or stock dividends. At the same time, economists say, they could help areas hardest hit by the housing crash reach a bottom of the market.