Hi
Go rolex. Sub, gmt or sd, at preowned no worries if you were to flip it later. Get the black bezel. There are plenty preowned to choose from the dealers in town. Get one that is relatively new full set from a reputable dealer.
Insist on a buy-back price w him in case you need to sell. That will give you plenty of options as you continue buying & selling.
I am into this hobby for 3 years. I started w rolex and didnt get hurt. Not that other brands arent good but thats the fact here.
Come to the gtg and surely, all of us can share our experiences w you. I agree w all seniors and as tyler said, its big money you are putting down
Sm