How should the contract be arranged? 

Older folks are used to that sort of arrangement.  

I would say 50/50 being this is your first arrangement if you trust them and their experience.

These are sometimes called parking arrangements.

but ONLY if it is a home with ADU or a shared living space (living areas, kitchen or bath) arrangement,  NOT if it is a legal duplex.

The brother in law was fine with the arrangements until recently.

When I wholesale to someone I've never worked with before and have no idea whether or not they will flake out, I ask for a portion of the assignment fee as a non refundable deposit.Not to be confused with the earnest money deposit  which I have already paid to the title company when the contract I have with the seller was executed.It's a common practice meant to keep tire kickers at bay.Most serious investors are fine with this arrangement, most who aren't usually turn out to wannabes....which is fine, everyone has to start somewhere, right?

I am on a steep learning curve on this as I had made an offer on a property in New Mexico with this arrangement. 

@Samy Nabhani Perhaps suggest such an arrangement to your broker on your next deal. 

Rental management company all ready arrange to take over, tenants ready to move in ready to sign a lease..