Need help on this deal

[David Tower]

This sounds like a purchase and then a lease option but I'm not exactly sure. I plan on bringing in a local expert but want to get BP's take on it.

Here's the details

owner needs to sell. lets say it's for 100-110k
owner's relative lives there and he only wants to sell if they can buy the house from me at some point in the future (6 months maybe) when their credit is better.
They don't need me to fix up the place and the tenant buyer would pay maybe 140-150

The current tenants would remain in the house. I may be able to line up conventional financing for my purchase. I don't think the house is worth even 140 with no work done to it but the tenants really want to stay there and would pay a premium (supposedly).

The owner's like me. they said they've been approached by more agressive people and were turned off but that I impressed them. I like them too they seem really nice.

How would you structure a deal in this situation?

Thanks