I've lusted after watches my entire life, especially Rolex. Over the last 20 years, I've had the opportunity to own some very nice pieces (and make a profit in the process).
Take your time and buy from a reputable seller or authorized dealer. It may cost you a little more, but it's completely worth it.
Here's a Youtube channel that has some great information on all sorts of watches.
Have fun!
https://www.youtube.com/user/theurbangentry/videos