More than 500 apartments are planned for Downtown Pittsburgh over the next couple of years.  Thanks to a credit crunch, most developers have switched their focus away from condominiums and are hoping there is a market for luxury rentals.   Fortunately, the Downtown Pittsburgh condo market was strong before the national lending crisis and Pittsburgh still has some successful projects, such as the Otto Milk building in the Strip and several smaller projects along Penn Ave.  Some developers are focusing on more “middle class” condos, where units will start at $150,000 and up.