Home built toy hauler

It can undoubtedly be done, as long as you have lots of time and a fair bit of money, and the necessary skills. Also a big truck to pull it with when you're finished. :) A 40' homebuilt toyhauler is going to be very heavy simply because the common person doesn't have easy access to the aluminum framing to keep the weight down.

And I don't know that it will hold up better since the average builder is also not an engineer and would not know how to figure out all the stresses involved in building for a mobile platform. I think building a toyhauler like you would a stationary house wouldn't necessarily hold up that well to the rigors of moving down a rough, bumpy road/highway.

If you have some special need not served by a production model or just like to take on projects...go for it.

The idea that mass produced units are junk is mostly a misunderstanding of design requirements. Our rig is 20yrs old and while it does require some maintenance, nothing crazy. Otherwise, it's perfectly functional and no reason we couldn't keep her going pretty much forever.

Most of the maintenance items by the way are in the mechanical systems (fridge, air/con, plumbing, etc...). You will have all those same systems on a home built rig and they will have similar maintenance requirements.

If you think you can make a one off unit cheaper, better and with decent resale value, you are fooling yourself. Most of the tiny houses I've seen are really meant to sit in one spot being massively overweight and not really designed for much highway use.