I carry 1 million for up to 3 stories. Runs about 60 bucks a month. You can easily get away with a 200k or 500k policy if your getting started. (Just the fact that you have insurance will separate you from many companies out there.
Larger Properties (hotels, mid rise may want between 2-5m) Property Management companies that I do work for only require 500k.
Either way its only a few bucks for to go for a full 1M in coverage.