Believe it or not, there are several opportunities to lease/rent to own. Unfortunately, we don't have a classification like that on the MLS, although some realtor will include this option on the remarks.
I've seen quite a few possibilities in craigslist. Enter key words in your search like rent to own, lease purchase, etc. Here's what I found when I did that search. http://sfbay.craigslist.org/eby/reb/1031002552.html
If/when you do decide to do a lease with an option to purchase, please make sure that you well-prepared.
First of all, your rent could be higher than normal rent because the seller may apply part of your deposit towards the purchase price.
Second, you may be asked to put down a non-refundable option money. If you decide to exercise the option to buy, the seller may apply this option towards purchase.
This option money may be in addition to the normal practice of having a security deposit and one month's rent in advance.
There are several resources on line that could walk you through the process so that you can best understand what to expect. Home ownership is the ultimate goal of lease/purchase option and as such it will necessitate a careful review of the terms, conditions, and disclosures.