Especially since it is the one I know something about.

Advantages-
1) You would own your own trailer and rent the space. This preserves the dignity of some independence.
2) The park could be owned by a corporation which would, in turn, be owned jointly by the residents. They pay rent to the corporation which then pays the bank.
3) For $500,000 you should be able to buy an existing park with 20 spaces in a decent location. Standard financing would require $100,000 down. So if 20 people are in that means they come up with $5000 each to start.
4) Monthly payments would run about $3000 or so. $150/month.
5) I am basing the scenario on a park I am familiar with and it has a young couple who live in a trailer furnished by the park. They mow and maintain and manage for their rent plus $400/month. A similar arrangement should be possible and duties to include cooking one meal per day for 20 added. Say $600/month. $30 each.
6) So that comes to $180/month each so far. Add in cost of food etc and you probably get close to $400 or so. Wild guess on that BTW.

So it is doable strictly by numbers. Reality might be harder though.