Mobile homes (now-a-days designated as "manufactured housing") have one thing in common with other houses and that is a wide variation in the quality of the materials used and in the quality of the construction. IF you get one properly built and IF it is properly installed and set up, it will be just as good as a site built house. The problem is that those two "IFs" are seldom met. I bought a very small, used "house trailer" when I was 19 years old and it turned out to be a good investment. Then I didn't live in one again until '95 when I bought the little farm that included a ragged old 14' x 70' mobile home with many problems. I fixed it up enough for us to live in a couple of years, then ordered a new double-wide custom built the way I wanted it, but I still made a couple of mistakes.
And 3 weeks ago, we bought another little single wide in a mobile home park because of the location and price, but it's a Fleetwood product (biggest manufacturer in the world and builds the cheapest thing they can get away with). Like some other things, not too bad for the price, but far from being quality.
Like Cindi said, don't let a salesman talk you into particle board floors (they have some other names for them and will tell you all about the benefits and how that's better than plywood); don't you believe it! Insist on plywood floors (yes, that will cost a little more, but well worth it). The plumbing is another major factor. Our last double-wide had all CPVC water lines, brass cut-off valves at the toilets and under sink and lavatories, Moen lifetime faucets; i.e., much better than the flexible stuff many use. Then are plastic lavatories and toilets good enough, or do you want regular home type (porcelain) fixtures offered at additional cost.
What kind and amount of insulation, of course, but then what kind of siding? Many were notorious for rotting along the bottom. Some now have hardipanel that is not supposed to rot and some, as our current one, have vinyl siding. What kind and quality of roofing will it have? Are you satisfied with the heating and air-conditioning ducted in the floor (limits where you can place furniture) or will you insist on it being in the ceiling (as we did with our double-wide)? Check the quality of the cabinetry. A few are very good; many are very cheap. Are you getting storm doors and windows, or at least double pane of some type? Are the walls paneled? Vinyl coated thin sheetrock, or as has been said, sheetrocked, taped and bedded on site? Is 14 gauge electrical wiring satisfactory or do you want to pay extra for 12-2 romex? Are mini-blinds or other window treatments included? Does it have 32" or 36" wide doors? Are they regular house type doors, wood or steel, or the mobile home type that open outward (usually aluminum over wood)? Dead bolt locks included? Ceiling fans? Pre-wired for telephone and/or TV/Internet coax?
Look at the water heater. Is it in a drain pan large enough to carry off the water if it springs a leak?
And finally . . . I would never put another manufactured house on my own property unless it was set up on a concrete slab for a foundation! It's quite common to put cinder block piers on a small concrete base and level with hardwood wedges. Unless you use the concrete slab, you can bet on needing to have it re-leveled periodically (had this one done yesterday) at a cost of $300 to $600 usually in this area. I know of one area in which manufactured housing is prohibited unless it is set up on a concrete slab.
Some good friends of ours have just sold their farm and bought two acres at the edge of town. They thought they were going to go with a modular until the price approached $140k, so to get all the same features and size in a manufactured home on a concrete slab is going to cost about half that. I suppose those price differences may vary in different parts of the country.
Good luck with whichever way you go.
