Regardless of the percentage of the coming drop, we are just at its beginning. No matter how good a deal you strike, you just pretty much set the roof for comparable pricing for a while. We have a few years to go for catching the falling knife is worth the risk.
As to what you are buying, condo conversions are old. They are mostly apts that will need much more maintenance over the years than comparable new construction. Are you buying into a community that will be willing/able to do that work?