Cheap/Durable Hull Material For Houseboat

There's a ton of things here to question, but add at least 4% cost a year for inflation while the project matures, and also the direct cost to live and support yourself while building full time.
Six months build time is not very realistic, it would likely be surprisingly longer than that.

 

Okay, so how long do you think it will take to build it?

If I have the money to do what needs to be done and I know what needs to get done, I'm not going to fool around. This design is really simple, so I have a really good idea of almost every step of the building process.

For cost of living while building I decided it would be a good idea to get a part time job to pay for basic stuff like food and gas.

This still allows me to work on the boat full time.

I have a travel trailer and a 3/4 ton pickup truck, I could park the travel trailer on the same lot I'm building the boat on. That eliminates rent.

 

Creosote is not banned by the EPA. It is “restricted” from the general public. You can buy it as an insecticide from farm suppliers and paint 100s of miles of fence posts with it. You know how much a “pesticide applicator license” costs??? Probably less than a tube of “marine grade” caulking from your NA/MS certified boatyard.

 

Creosote is banned for residential use. That would include the interior of the habitable space in a boat.
Creosote | US EPA https://www.epa.gov/ingredients-used-pesticide-products/creosote

 

I wouldn’t “treat” wood. As a “qualified pest applicator” I would spray (into a soaking puddle) my lumber for termites. Just build the house boat out of old railroad ties. You can still get them wholesale for about $8 each. $3000.00 per truckload in Grand Island, Nenraska.