Like any collectible, the market for used products surges and sinks, and reproductions may suit your purposes just as well. Though Howard Lamey and Paul Race would encourage you to take a crack at building your own buildings, you may prefer starting your collection by buying a few. Especially if you can find good deals or buildings that would beyond your skill set for now.
However you choose to populate your putz, consider that a few nice houses will be more fun to set up and view than a score of damaged, cheap, common little houses. If you have a more developed sense of design, you might also consider color and style as you shop, so your putz village meets your current aesthetic needs.
The following pages have recommendations on buying used and new putz houses.