I used to be a Realtor. I have also been a renovator of older homes.
Modular homes are generally of of a higher quality of construction than conventional north american wood frame homes, as they have to actually move when being delivered without falling to pieces. 
What margin of error are you allowing? Like lines and points, it seems to me that squares and right angles are mathematical abstractions that can never be reached in the real world, only approximated. The only question is how closely the approximation approaches the ideal.
Are you speaking of older houses as well as new construction?
When I was a kid, I helped Dad put plastic tile in the bathroom.
At some point we had to replace the panel in front of the bathtub.
On the back was written, “Give to Bob.” 
Speaking from my own experience: a mobile/modular home built since, say, the late nineties is a very different animal than the ones built during my childhood. As a kid, my family lived in a 1972 (no idea what brand) doublewide, later a singlewide of about the same vintage, and later still an early/mid-eighties doublewide. The first was far nicer than the early 1900s home we moved from, but the quality was terrible. It had electrical problems from the start. I don’t recall any similar problems from the second, but the pressboard sub-floors were a big issue. A wet towel on the floor could result in major headaches. We didn’t live in the third for very long, but it seemed significantly higher quality than the previous ones.
Currently, my mom owns a 1999 (no idea what brand, but I know it’s a smaller operation out of Florida,) modular, built to install on a foundation. That sucker is solid: marble windowsills, roof vents vs. floor vents, etc. She’s owned it since about 2003, and has never had any major issues, although her original appliances are finally being replaced, plus she removed all the carpet and installed laminate, and replaced the giant tub and small shower with a giant shower and a linen closet.
Over the summer, my husband and I purchased a used 1999 Fleetwood modular with a 12 x 20 addition. (Plus a new metal roof and 450 square feet of covered porches.) We had it moved, and are almost finished with an overhaul - new flooring, paint, redone kitchen, etc. By the time we’re all done, we’ll have about $95000 invested in our home, land, well, and septic system, plus whatever we spend on a barn. Around here, a comparable 5 bedroom, 3 bath stick-built home with almost 5 acres, just outside city limits, would have cost a minimum of $150k for a major fixer-upper, $200k+ for a dated home with the zoning our land has.
I will say these two things: the manufacturer makes a big difference, so do some research, and the best thing about mobile homes? Their floor plans are typically very very good -efficient use of space.
My mom has one that was built and placed in the mid-ninties. One time a few years ago, my brother was replacing/repairing some shingles and noticed they hadn’t put the bolts in along the roof line that hold the two halves together. The thing also seems to be settling odd as the floor seams are not lined up any more.
As far as insulation, he ended up taking all the siding off and removing the old ‘buffalo’ board and replacing it with the modern style sheathing. It made a world of difference.
Another thing, hardly any of the doors will latch or stay open.
The company did a very poor job at setting this one and it shows. Otherwise it would be a very nice house.
Did the seller’s people put it together, or a low bid contractor?
My parents had a 3 bedroom rancher built by a factory on Maryland’s Eastern Shore & delivered to the property in two pieces. Once there the 2 peices were winched together, and then the roof, end walls and other odds & ends were completed.
Nanticoke Homes was the company.
That was almost 30 years ago and I have never seen a more solid house. True angles, tight in winter & summer. The only way people can tell it is modular is that the central load bearing wall is double thick so the halves could be transported.
It all depends on the manufacturer.
Surely much depend upon who puts it together.
I don’t know for sure, but I think it was the place that sold it that also set it. Or it may have been someone they hired.
So, did you go look?
Property value is land plus improvements (the house or unit itself). The improvement gains value with inflation and loses value with obsolescence. Manufactured units go obsolete faster than houses, so they don’t retain value as well.
On the other hand, because the initial price is so much lower, the improvement (unit) is less of a percentage of the total value of the property. That makes land value more important to manufactured units. Land value drives real estate markets and goes up and down based only on market value. For manufactured units, the gains in land value, especially in rural areas with acreage, septic, and wells, is how your unit will go up in value.
The biggest problem with reselling a manufactured unit is financing. It’s much harder to get financing for manufactured units than houses, plus foundation requirements (the tie down of the manufactured unit to your land) can change or sometimes be ignored by the installer. This limits the amount of buyers you can get, which lowers value.
Overall, I’d avoid trailer parks and make sure it’s either in a good subdivision or an area where land value is fairly stable. Over time, you should save enough in mortgage payments plus see enough gains for it to be a good buy. And some of the units now are awesome…
PS Also, you’ll blow away in a tornado. Nothing can be done about that.
I am from there, and I was going to say that modular homes were pretty much standard/accepted as “regular” homes when I was a child around 30 years ago. In the mid 90s my mother explored buying a new home or having the home on her property replaced. We were/are pretty close with a couple home builders/developers and a few notable real estate people, and most of the options we were given (and many of the new developments going up) were modular. I seem to recall “Nanticoke Homes” being used generically to describe modular homes. Though there were other companies, like Shawnee and some others I don’t recall.
I live somewhere else now, in a “stick built” house in the MidWest, and after less than 20 years it’s falling apart everywhere.
.
Tornadoes.
:dubious:
A 48" floor cabinet shouldn’t have a 1/2 inch gap on one side when put flush to one wall in a corner. I expect the wall itself to have some minor error because of warped 2x4’s but the footer should be dead on. Once you get one wall out of square the rest of them follow.
houses built on jigs tend to be very square. As I said before, my garage roof trusses came delivered like they were carved out of a single block of wood. I ran a line along the edge and everything set perfectly.
Then you have some piss-poor carpenters working whereveryouare. Unless you’re taking about a very old house. If you walked in to any new house I framed, you’d be welcome to pick up a framing square or level and slap them on any corner you liked.
And pre-fab roof trusses, the ones I’ve dealt with anyway, are made with the nastiest shit they can get away with.
Guy I worked for actually worked in a pre-fab factory for a while. They had STATED tolerances of 1" out of plumb on 4’.
Only if you’re making the biggest layout mistake ever.
Were they making cheap storage buildings or something of that nature?
Nonono…aforementioned dwellings.
A customer wants a floor cabinet installed. There is no “layout mistake”. I just gave an example of what I routinely see in stick built houses. I also gave an example of jig-built trusses. They were extremely precise in their construction. By default, a jig built item should deliver consistent tolerances.
Well good for you. Seriously. But I can go through neighborhood after neighborhood and show you shoddy workmanship after a storm because shingles weren’t put on correctly. In the real world, houses are knocked out but people in a hurry whether it’s stick built or jig built. Jigs make a more consistent product.