I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear about your situation.
You have the same legal right to the trailer that you do. He can't just take it. At the same time - you don't have any legal right to keep him from it either, because it belongs to both of you. If he shows up to take the trailer out of the where you've parked it, you can call the police, but you can't be there all the time (and shouldn't have to be). Usually, when two people buy property together and break up, one of two things happens: either the person who stays behind buys out the other person's interest, or they sell the property to a third party and split the money. This can be achieved by a Petition for Partition, which is filed in the local courthouse. He'll be required to sign the title over to you as part of the case.
If you're going to buy him out so you can continue living there, you can ask the judge to order that you be allowed to pay what you owe him directly toward the loan that your ex was supposed to repay and is now claiming that he won't. Or the judge can order that his share of the money be put into an escrow account, held until the loan is paid in full.
The other option is to sue him for any payments you have to make on the loan to protect your own credit, but it may be a lot easier for you to do everything in one case at the same time.
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