Generally, I don't think that the final product is what they had in mind to start with. From what I have seen, it goes more like this:
1: Buy land
2: Need house quickly, get trailer, maybe build a house later.
3: Until the house gets built, it would be nice to have a little deck. Doesn't need to be fancy though- 2x4 framing and scrap plywood decking should be fine.
4: Let's build a porch roof, time to get some more 2x4's and roll roofing.
5: We need some more living space, let's completely enclose the deck. We will use those old windows that we scavenged up, should work fine for temporary.
6: Looks like the family is getting bigger, maybe I should put an addition off the other door. What kind of building materials can I scrounge up this time?
7: It sure was nice when we had a deck, maybe we should build another.
8: See #4, #5
9: Hmm, the roof is leaking, I'll just frame over it, to get us through till we can build a house. 2x4 rafters should be fine for short term, and I'm pretty sure I still have some more roll roofing around here somewhere...
10: The aluminum siding on the south side is giving out, t-111 should do the trick. After all, we should be able to afford a house next year.
11: We need some more storage space, so maybe an addition off the addition is in order.
12: Yaa, inherented some money! Finally, we can build the house!!!
13: I bet it would be cheaper to make this place look like a regular house...