I suspect that you'd be much better off by buying a used rig and retrofitting it, as opposed to creating your own.
As others have mentioned, many (if not most) RV parks and resorts won't allow something homebuilt to pass their entrance gates. Plus, most have a 20 year age limit, some have a 10 year age limit. Much like the clique of cheerleaders in highschool, appearance is key.
There's the question of overall length as well - you're limiting your destinations (and where you can stop during travel) with a rig that long. And weight; always be aware of the mass of what you'll be travelling with (and the fuel you'll be purchasing).
I suggest you flip your whole full-timing quest on its ear. Where do you want to travel to? Where do you want to explore? Where do you want to stay? Look at what others travel in, look at restrictions (age, length, type of rig, etc) of the places you want to stay - and start thinking about what kind of rig best suits your dreams.
