Lease/Option is very dangerous way to go:
The Buyer is usually desperate and the Seller knows it.
There is no "boilerplate" contract, so that means involving an Attorney.
Plus the Contract can be written any way the parties want.
You will be guaranteeing that you will buy the house at a definite time in the future, for a predetermined amount.
Do you KNOW where you will be 3-5 years from now, financially and family-wise?
Do you KNOW how much the house will be worth in 3-5 years?
You will be betting thousands on those answers.