The official web site has lots of information, and is a good place to start: http://mtlebanon.org/
There is a strong resale and rental market there. I just sold one in neighboring Whitehall, and have a couple active clients searching there, so I've seen many of the properties currently on the market. I used to live in the South Hills (South Park, then West Mifflin). Let me know if I can help you further, and if you have any current real estate needs. I'd be happy to assist you.
Mt. Lebanon and the South Hill area including Upper St. Claire are areas that offer many different types of residential living options in many price ranges as well as retirement communites.
As a Realtor with Coldwell Banker, I have sold many homes in this area and I would be happy to assist with answering any other questions and assisting with your real estate needs. Please let me know what price range and other specific criteria you are looking for. I look forward to assisting with your questions.