I am afraid to count my lenses as the wife might find out how many I have and kill me!! LOL Actually I've bought over 60 and have resold or given away a lot of them. I'm in the process of collecting the entire run of T4 and TX lenses. This last one is not as common as some and therefore a good addition to the collection.
I've had 3 bad outcomes in all those transactions and most of the time it is because the people selling the lens cannot give me good info on the lens. Sometimes you have to guess at the type of lens mount from observing the blurry photos they supply. Ask questions and research the lens you want to buy. Go slow and cheap at first and then move up to a higher cost lens. If in doubt about a lens ask here and we will try to help you. A lot of knowledgeable folks here. They have helped me a lot.