Well, this usually works in highly depressed markets.
It also usually works in favor of the landlord/owner.
This is because rent in this case is higher, an option (usually non-refundable) needs to be paid,
the term to buy is a year or two (short) and so most tenants end up loosing their option money and unable to save up on top of their already higher rent.
I see the R2O allure being used when a buyer really wants to rent something good that's on the market for sale but is not selling. It's a buyer's way of getting the place, but rarely a purchase comes through...
The idea that the buyer would benefit by "locking into" a lower price while saving money is a good idea, especially if the real estate market is recovering in the area. But, to make the purchase happen, you'd need to conscienciously "risk" your option funds and you'd need to be on a very disciplined saving project for the period of your option term. If you are sure that you can handle it - go for it!
Any agent can call the prospective sellers and ask about owners being willing to R2O.
However, it's a lot of work for your agent, so the houses that have been on the market for a long time (but not short sales) are better candidates for your purposes.
Hope this helps,
Beachfront Realty, Inc.