Easy Money-- When you unlock the Ford GT Concept, buy it for $150,000 and then sell it for 185,000 or 195,000 for an easy profit. Also, when you win the Tipo 33/2, Sell it for 800,000 and you will get a sale in a maximum of about 10 game-days. You should get $1,127,000 for it.
Fast Drag Races-- Get a six gear car. When you start off the drag races, you shift all the way into 6th gear, then when you reach about 40 MPH you want to shift back into 3rd gear and then work your way up the gears.
NOS-- You have to go to the drag races and lose on a day ending with 5(305, 15 etc.). Then, after you exit out, go to the used parts shop, and all the way at the end should be some ????. Thats your NOS.