What happens when someone holds my personal stuff because that person thinks that I owe them money?
It sounds like it could be illegal, but you are being too vague to offer any real answers. If you are a tenant and the landlord/owner is holding personal items, then it’s probably illegal. If this is just a personal debt, it’s illegal, unless you have a contract stipulating the ‘personal stuff’ as collateral of some sort. Storage units can sell stuff at a certain point, if you stop paying the rental fees. If that’s the case.