If it has been a lot of years since you last rode a bike, you are probably going to be suffering from sticker shock when you visit a bike shop and find that the price range for bikes with entry level components can reach $500. What you get with a bike shop is likely a bike that fits and has a warranty this is worth something. Many bike shops carry used bikes.

Finding a bike on CL is a crap shoot. Even if you know the proper frame size (which will be different for different frame types) a lot of sellers don't list the frame size or don't know how to measure it. I just finished looking at nationwide CL listings for an entry level recumbent trike for someone. The CL prices were crazy. The MSRP for the two models were $1000 and $1,300. Almost all of the listings were within $100 to $200 of the MSRP. Used bikes have no warranty and are sold AS IS. You would have to be nuts to pay near the MSRP for a used bike.