In league 5, but also in any other league there are "last man standing" events where all you have to do is spook all the other cars into hitting the wall, and you win.

Start with just a bit of money, 5 to 10 thousand, enter a LMS event, pick a driver to bet it all against, and as soon as the race starts get on 'em immediately and spook 'em into a wall.

Even if you lose the event, you get the bet money as long as you take them out first.

Super easy money, just don't hit a wall, and you can bet multiple drivers per race and make 100k just off of bets. Have fun!