The best start car is the Cobalt SS. Use that car until you get the Eclipse. When you win blacklist races, try for the three '?' markers. You can get cash or the pink slip car. If you get their car, go to the safe house and sell it. You can get good money by doing this, and get unique upgrades after you start getting into the visuals (after you switch from the Cobalt).

After beating Blacklist #8, you will have a choice to buy the Lotus Elise. At this point you should have enough money to buy it. If not, you may want sell to get enough money. Once you have the money, buy that car. It is great at road handling, and is very fast once you have maxed out its performance. Note: The stock top speed and handling do not look high at first.