You can still get a rank without spending irl money. For example if you amount let's say good stuff or lots of money in a gamemode, you can do what's called an irl deal. It works by you getting someone to buy you a rank and you'll give them the stuff for doing it.

When you do an irl deal, the person paying irl money always goes first because they can get their money back, and this way, you convinced someone to pay money to the server.