Multi-unit buildings became one of the most over-heated markets during the bubble city wide. "Investors" thought they could convert all of them to single family homes for bigger bucks. Many people were able to buy two and three flat buildings due to loose lending based on the inflated incomes stated by the rentals. In the heated market the purchase numbers barely made sense for owner-operators and the multi-units were a good mark for mortgage fraud for "investors".
Today however with ownership versus renting parity improving, there are good deals in multi-units for owner operators again. Buying a two or three flat rather than a condo may afford you a yard, garage, basement and the tax incentives of owning while your tenants help pay the mortgage.