See my misadventures in Barclay Ridge. These condominiums are converted from apartments - which means, at least for the 2-level units:

• The kitchen drainage and sewer pipes run through the master bedroom walls. You will know when your neighbors use the toilet at night.
• The windows are stuck in their frames - only a few actually lift up easily. The management told me this was because of the February 2001 earthquake. So why didn't the windows at my previous condominium (I rented from the owner) have problems?
• Walls are thin. I can hear my neighbors snore, and the upstairs and next-door neighbors running their garbage disposal.