Since the trailers are already there, this info might not help, but I dated a guy who would go to foreclosure auctions and buy 1-2 year old single wides for an average of $7K. He owns a lot of property in an area that is lenient on trailers (many are not). He spends a few hundred recarpeting, hooking up utilities, etc. He rents them out for $90-100 a week with no lease. You're a week late, your stuff's outside and the lock's changed. Mostly he rents to Mexicans who work in the carpet mills in Dalton GA. He's in the black in about a year and a half and the rest is gravy. His stepfather handles the maintenance and old boyfriend who's a big fellow, handled the collecting every Sunday.
They are QUITE the money maker if you don't mind dealing with the type of people who rent trailers
If this is a vacation type place, then I know nothing ;)