“This used to be one of the worst houses I’d seen,” said Jason Williams, who rehabbed the Washington Heights bungalow with his wife, Esther, after buying it from the Cook County Land Bank in August for about $17,000. “We had to do everything to it, all the way down to the studs.” The Williams’ foreclosure rehab firm, Ultimate Real Estate Group, put the house on the market in early November, asking $154,900.