If I read your post correctly, you're thinking along the lines of a metal barn or workshop building and finishing the inside off as a home. You can get the kit or have somthing like that built fairly cheaply and quickly from your local supplier.
Just be sure you are comparing apples to apples on prices. Each supplier varries the guage of steel or finished siding or roofing to get the price down. Some kits are engineered for certain wind loads, and others are nothing more than a basic shell.
I wont give names out, but their is a member that I met at the Tejas get together who did exactly what I'm describing.
Some people do this just for the tax advantage of not having their ag land change to residential when buildig a place to live on it. Some have done this in order to have a quick place to live and have barn space for a workshop and storage of equipment all in one building.
The layout is of course up to you and your needs. I like to use a drafting program when considering layouts because I can put in furuniture and fixtures to get a feel of how the space will work when its done.
For example, you can place your toilet in the bathroom and see how much room you have for standing in front of it in the program. I've seen bad layouts that failed to consider this, and it became a problem after the toilet was installed.
I use the Broaderbund home design software. It works well and is easy to learn. There are others to choose from, but I'm not familiar with them.
Be sure you have your layout planned out before building, because its extremely important to have your plumbing in place before pouring your slab.
Once the building is up and sealed in, it'll be an easy process to stick frame your walls and finish it out.
I'm not a fan of using metal framing as a substitute for stick framing. I've heard all the arguments for it and some against. I think stick frameing is still a far superior method in building a home and will remain so for many years to come.
Mobile homes are probably the worse investment you can make. They depreciate the day you buy them. They wear extremely fast compared to a conventional home. A brand new one is almost as expensive as a stick built home and resale absolutely sucks. You can find a deal on used ones, but you better know how to fix it up and do repairs. Most are put together with inferior materials with a focus on light weight and minimal quality.
I personally know several dealers of mobile homes and what they pay for repos and their resale markup is at least double, and in many cases, they triple the price they paid for it. One of the biggest money makers for moble homes is selling to people who cant afford them just so they can repo it and resell it again. Many mobile homes have been repo'd three and four times before getting in too shaby of condition to do it any more.
You're property taxes will increase significantly when you add a moble home. It will be considered a home and taxed accordingly. The sales people at the mobile home lots never tell the buyers about this!!!!!!!!
If you're thinking of building a house, use $50 to $60 a square foot as a general rule of thumb. And this is the total finished home with carpet and cabinets installed ready to move in. Another general rule to remember is you can dry in a home for around $15 a square foot, then take your time finishing it off yourself over time.
Remember to add about $10 a foot to the price when you go to the bank for a loan. If you come in at a wholesale price to build the house and you don't have a track record with them, they will think your cutting too many corners and wont grant the loan. Banks are funny in financing construction projects. They have some numbers that they consider the normal range, and you need to be in line with what they consider normal. You don' thave to spend the extra money, nor do you pay interest on anything you don't actually spend.
Last house I built cost $90,000 for 1,866 of living area plus a two car garage with landscaping included. I had $22,000 still available on the construction loan. I only paid interest on the $90,000 until it sold.
Another option is building a pole barn and finishing out part of it to live in. That's what I did. I have a thread in the projects section called "My Container Barn" wich might be useful if your interested in that route. Price is a little tough to figure because it wasn't originally planned as a place to live, but became a forced issue with my divorce. I know I was well under $20 a foot including appliances and funiture.
