I lived in a mobile home for about 6 years and I don't think I'd do it again. Everything is cheap and hard to work on. They use 1x2s instead of 2x4s. The drywall is like cardboard. The underside is made of plastic sheeting! I never figured out how to fix that crap underneath without it falling apart after a few months. Duct tape falls off in a few weeks.
As far as I can tell the shed I'm looking at uses the same construction as a normal home. The model I'm looking at is specifically sold as a cabin. 2x4s every 16", 2"x6" floor joists, engineered wood exterior panels, etc. I'm nowhere near a construction expert but when I look at these sheds I can visualize how to work on them, they're so simple.
Sounds like you needed this:
https://www.amazon.com/Mobile-Belly-Bottom-Repair-Fix-Underbelly/dp/B00BJ5SPO8
But yeah, it also sounds like maybe this shed is ideal for you, and that a mobile home wasn't. You know yourself best. Everybody's different! Just keep in mind all the little things that can go into making a house really look finished and "right." Not to mention work correctly.
Electric. Don't forget the dryer.
Plumbing. Don't forget the washer.
Don't forget the venting
And then flashing, sealant, etc., to seal up the hole in your roof really well (you could vent out of the top of the wall instead -- I came up with that great idea years ago but never have tried it)
CAT5 or other network cabling? (optional)
All that you've got to do
before putting up the inner walls. Then
Insulation
Walls. This could be paneling instead of drywall, by the way. That's one thing mobile home manufacturers got right in the '70s, in my opinion. Big labor saver.
Ceiling. Once again here: drywall is heavy and time-consuming. You might consider the various alternatives.
Flooring. Cushioned vinyl sheeting is a good, easy option, especially for your situation: one big rectangle. No fancy cutting. You don't even have to glue it down. If you're going to separate into rooms, you can again steal a page from the mobile home playbook and lay the flooring first, then put the interior wall(s) on top of it.
Trim. Trim, trim everywhere.
More trim.
Endless trim.
Tons of other finishing touches you never thought of. House-grade windows go in that list somewhere.
If it's just for you, you can always cut corners and rig something up that's good enough. You'll get used to it. That's the danger, in fact. If you don't finish it all at once, if you're living in it as you work on it, chances are you'll never finish it. You'll get to a point that's "good enough" (but pretty bad) and then take a break for a week, then a month, then.... why did I think I needed trim again? Or that this stub of pipe isn't good enough as a kitchen faucet? Hey, it works!
