You can sue them for the unpaid rental fee and/or the cost of the unit the then-current fair-market value lawsuits are how you recover property which others have taken or withheld from you, or money they owe you pursuant to a contract. d on what you write, you should have a good lawsuit you would need to show, by documentation and testimony, that they had an agreement to pay for rental and failed to do so and that you were the owner of the units which they have failed to return. Assuming you can do so, you would receive a judgment ordering them to pay you compensation.