Not many in Texas. Texas has certain laws that make lease-options (or rent-to-buys) difficult and tricky to do. The other 49 states are fine. It's just Texas. If you want to pursue that, make sure your agent knows exactly what he/she is doing, and has done other such transactions in Texas.
Here's a blog I wrote on how to find lease-options/rent-to-buy homes: http://bit.ly/findaleaseoption
However, again, make sure any agent you select knows precisely how to comply with Texas law.
Hope that helps.