You have to look up the laws in your state, but here in California, we would give him a 3 day notice to perform covenant or quit, meaning he has 3 days to get the vehicle removed from the driveway or he risks being evicted from your property. As far as not having a lease with him, you may also serve him with a 3 day notice to review and sign your lease. You can get a free lease (and any variety of forms) from www.aoausa.com. Click on free forms, and scroll down to rental leases.
If this guy is a good friend then he should understand your concern and move the trailer to a more appropriate place without having to take any legal action. Maybe you can do a little homework first, and see where he is able to store it, like a parking spot he could rent close by that accepts them.
I think it was Benjamin Franklin who once said "guests and fish have one thing in common, they both stink after 3 days". Good luck!... more