What to buy? Stucture, permit, easement?

Hello, I want to buy a billboard - I just dont know to buy. Do I buy the structure, the permit, the lease, the easement? What is the best deal to structure? I would think that owning the easement, structure and permit are the best thing? But most of the signs that are for sale do not include these - its just the cash flow from the sign company like CBS or Clear Channel - at the end of the lease - you dont own anything - because the sign companies but up the structure and got the permit. I dont know if this is worth owning? Does anyone have any experience with how to structure a deal?