dh is thinking of buying a small house for investment purposes. (rent it out)
He wants to pay for the whole thing so no mortgage
what other fees are there besides for taxes and insurance?
Monthly? The water bill may be yours if you're in NYC. And there will be closing fees involved even if he doesn't take a mortgage out. Most financial planners would recommend a mortgage though rather than buying cash and having all that equity there when you can be using it for other investments.