Love it for its driving, hate it for its economy, that in a nutshell is Forza 5. Turn 10 is trying to change that though. With the new Forza Rewards program, you'll get a nice chunk of in-game money to use on cars, especially if you've previously played other Forza titles.
Tied to in-game progression, everything you do in game from unlocking cars, to performing perfect passes, will net you points on Forza Rewards. These points will get added to your overall point pool and advance you in Tiers. Each time you advance, you get a nice chunk of change to use in the game. New rewards will periodically be available, so checking back to the site is recommended, if you want the most bang for your buck.
You can head over to the Forza Rewards page now and log in using your Gamertag. If you've played any previous Forza games, they will all be displayed there along with all your points accumulated thus far.
It's a neat system that rewards players who stuck by Forza for many years instead of making them spend real money on Tokens.