It's incredibly cheap, but you need to spend some time doing boat-things like painting fixing rust, etc. Timewise it's probably comparable to a house.

I bought the boat in Holland for around $50.000 in cash and spent around $10.000 fixing it up with insulation, heating, toilet etc. So basically all I pay now is marina rent ($100 a month) and diesel for heating and electricity.

This is in Copenhagen btw.