Do you have lake access that is yours or a relatives? If not figure on renting a spot to keep it docked when not in use.
Since it will be HEAVY and BIG, keep that in mind for moving it. Do you have a trailer? Will it need to come out in the winter? Where will you store it in the winter? If you have no where, add storage into the costs.
Not trying to discourage, just trying to bring you down to reality.
If I were to build one, I would either live on the body of water I wanted it on, or I would rent a seasonal site at a campground or something similar so I could keep it docked.