Don’t be impatient; you may fall for/be obsessed over the first Rolex you see and want to buy it immediately; don’t - Rolex made over half a million watches in each of the last 25 years. Do your research, bide your time and find a source who you trust; it will be worth the wait.
Don’t fall for a ‘marriage’; sometimes you will find a 1980s watch with a 1970s dial or Submariner with a bracelet that was only ever used on Explorers. Whilst it may be attractive, it is wrong & not only will it be hard to resell, once you know the truth, it will irritate you every time you glance at your wrist.
Don’t skip your research; there are literally dozens of books on collectable Rolex watches and even more websites, take your time, do your research, and talk to dealers and other collectors before taking the plunge. No hour spent on research is a wasted hour.