What are potential issues with private money lenders?

[Billy Bob]

I'm considering using a PML and putting up a rental property I own out-right to buy another investment property for cash. It would be a 50% LTV. The lender would be the mortgage holder on the Deed on the property I own, but not a new one I buy. It would go through the "Lender's" title company. In a year or two I have some money coming in from a family estate and will pay it off. What are some of the pitfalls in dealing PMLs and how do I make sure I won't lose my property (besides defaulting) or put myself in a bad position? What happens if at the end of the term I pay off the lender and they don't release the Deed? Anyone have any horror stories? Any legal advice aside from having a RE Attorney look over the contract? Thanks in advance!!