They're a financial trap. So MOST people buy a home with finance, it might be a bank, credit union, or whatever but ultimately these loans are backed by larger organisations in the background that set the rules.
One thing you may not be aware of is that once a trailer park home is 15+ years old a LOT of companies won't loan against it. Even for a new dwelling of that type it can be hard to get finance, but as they grow older loan providers vanish.
There's a whole host of reasons for this (e.g. the type of people that live there are "high risk," the home can literally be stolen, there's less standardisation for home inspection, the land is low value since it is often in the middle of a trailer park (i.e. has no general purpose value)).
I call this a "trap" because you'll buy the trailer park home, then at some stage in the future you'll want to resell it; when that occurs you may suddenly find that while there are a lot of interested buyers none of them can get finance(!) to buy your home.
This has nothing to do with a buyer's credit score by the way. It is the property itself that won't be loaned against (since when you mortgage the property itself is normally collateral in case you don't pay, in this case they cannot determine that the property is worth as much as the loan you're asking for).
I know someone who's been trying to sell their trailer park home for a year. Lot's of interested buyers, all with good jobs and solid credit scores, but none of them can get finance because the property is too old, and none have the cash. They're tried dozens of financial institutions.