Yes, houseboats are nothing new. While it's true if your purse is deep you can buy a houseboat mansion,
actiually they can be - in smaller sizes - relatively inexpensive. Take a look at the offerings in yachtworld
to get an idea. A plastic or aluminum one can be bought for a small fraction of what a condo or coop would
cost. But, if this is your cuppa, the issue then becomes: where do you keep the boat and what's the cost?
Turns out there are a lot of places (for instance, in the SE) but then - as you say - you have to pay for dock space and
utilities - which can easily be equivalent to rent on a small apartment. Now, if you knew someone with a private
dock who would let you keep a boat there (let's say in exchange for keeping an eye on their house) then the
total costs could be quite low. One variant might be to buy one which comes with a trailer and live aboard during
the winter and store the boat on land - in FL, SC, or GA, for instance - when you're enjoying the summer in Maine.
Another variant would be to live "off the grid": for example, without electricity, or with modest electricity
provided by alternative energies. I have some friends for whom this variant would be very appealing. Not
what I'm looking for but....

btw, you can get a lot more boat for the buck by buying one of these used than by buying the much
smaller boat Tom referred to new. Plus, you can buy one cheap out of plastic or aluminum rather
than out of wood. Wood, after all, is only the choice of people who are dirt poor, and/or who don't know
better and/or who are nostalgic, hopeless, eccentric romantics.

Jerry