You might also want to check and see if there are any local ordances about any restrictions on the number of trailors that can be put on a property with one septic tank. As to the cost, he's right at minimum with no take down or set up at least $1500.00. You'd have to have it ready to go when they showed up to pull it out and the site prepped for the set up on your property.
The septic tank question should be answered first as you would be out the money and unable to hook it up to septic tank if you did it and were found out.

Good Luck