just look at the number, a 5 acre park can easily house 200 units, at $300 per lot, cash income is $60k per month, the only utilities included is water.
the con is up front cost, 5 acre ground with proper zoning cost about $250k, road and under ground utilities (electrical, gas, water, sewer, cable, phone...) about 600k-700k. bank don't like to financing this type of investments, the most bank do will loan be 50% of the ground, so you need 800k upfront.
I have a friend owns one, huge money. this guy was a body shop owner, now retire, own about 150+ units and a 100 space trailer park.