A different way to approach this may be to find a set of plans for a
houseboat design that fulfills your requirements, then purchase a set
of study plans (typically under $20) and see if the construction
materials / methods specified on the plans are within your ken.

For example, at:

http://www.boatdesigns.com/departments.asp?dept=7

You'll see a number of houseboat designs, some of which are plywood,
others fiberglass, others steel, and some that offer you a choice
between these methods.

My point is that the designer has taken the 'materials' into account
when the boat was designed; your only task is to reason whether or not
you're comfortable with the material specified. Once you alight on a
material (wood, glass, steel, etc) there are many useful books that
will help guide you.

MW