S and P, Case-Shiller shows prices off 35.1 percent from peak
CoreLogic: First month-over-month increase since last summer
OwnAmerica provides tools and training to serve growing market segment
Market watchers warn 20% to 30% return on investment is unsustainable
Colorado, Virginia, Texas and Florida dominate list
Nearly half of all sales are distressed
Company offers "HomeScore" ratings for foreclosures