How to determine future purchase price of a home when doing a lease option sandwich

[Charlie Gonzalez]

Good afternoon BP,

I am a new investor starting out my business model with lease option sandwiches.

My question is: how do I determine the future value/purchase price of a home when structing the lease option sandwich agreement? Is there a tool I can use to propose a future value? Or would a realtor have better insight on this matter? I would rather not just propose a random future purchase price. 

Lastly, how am I able determine the future purchase price I have with the seller, and the one I have with the sublessee/tenant buyer?

Thanks and please let me know!