I have a feeling you don't truly understand what is involved in a lease with the option to own.
To be brief - the sale price is usually set NOW, not when you actually go to purchase the house - do you really want to lock in a price for the future?
You also have no idea what the rates will be in 2 years.
Another very important part is that you will have to give some NON-refundable upfront money.
If you don't have a lump sum to give, you will pay an amount of money OVER and ABOVE the normal rent. That overage is the amount that will be applied to the purchase.......or forfeited if you don't buy the house.
I think some people in your situation mistakenly think their entire rent will be applied to the purchase. This is not usually the case.
Here is the problem...........if you don't qualify now (which is what you stated ) then you better make darn sure you will be approved for the loan 2 yrs from now.......and that the house will appraise out.....or, you will lose that upfront deposit.
Save up and get your credit and income where it all needs to be so you can move forward with a purchase when the time is right.