theres a cool way i earn $$ for console,and I dont see why it wouldnt work for PC too.You need an 8gig memory stick.format it for the game.thats first.
then,go to a straightaway near the airport,(best way I know to do a quick challenge).
OPEN MENU AND DO A SAVE TO YOUR STICK.
GO INTO CHALLENGE EDITOR AND CREAT A TIME TRIAL A LITTLE OVER 1.5 MILES.
test drive the challenge.
go to transfer,and make the purse 1 million.
scroll down and make it so that it is only available to club members,(here is where you need to be in a club where you can trust everyone,or make a club of your own just to make money).
upload your challenge.shut down your system immeadiately,(without ssAVING).
when you fire up the game again you should still have the money originally taken from the acct.
do this 3 times a day..
I know it works for console, and theoretically should work for pc too.Its not cheating,just taking advantage of the games parameters,(rules)