There are many tools out there to buy and sell RAM. The tool, eosc (https://eosc.app), that we created will allow a user to do this, as well as most EOS-specific wallets.
As for being paid in RAM for voting, this would be the first time I've heard of this so I think you might have misunderstood something. Feel free to send me a link to something you've seen that said this and I could gladly verify for you.