[QUESTION] Vintage Rolex Buying Tips

Hello, I am looking to buy a vintage Rolex as my first watch in the 3-4000 dollar price range. I’ve looked around and most of the Rolexes are from either the late 60s or 70s models which I am fine with. Are there any things I should be looking out for when buying (red or green flags)? How long will this watch last me? How do vintage Rolexes tend to hold their value? Thank you.