. >> reporter: frank rolfe leads a three day seminar.40 trailer parks and is an expect as squeezing money out of some of america's poorest people. >> to be in this business and really believe in it, you have to be a pest mist by nature. you have to put all of your eggs in the basket that the economy is going to continue to go down. >> reporter: he tells buyers to tear out amenities like play grounds which cost money to maintain, and to raise rent as high as possible without forcing residents to leave. >> there are no regulations at all. so basically the park owner is free to raise as much as he wants. >> reporter: investors are eager to get in. >> from a management standpoint, they are awesome, they have a very good return on the money, better often than an apartment building with a lot less management. >> reporter: a used trailer can cost a few thousand dollars, and the ground rent in a mobile home park like this one averages around $250 a month. many trailer park residents earn minimum wage are disabled or elderly living on fixed incom