Need For Speed Undercover

I'm a bit confused by the question, but here is what I know about Undercover when it comes to cars...

When you start off for the first time, you are given a limited selection of cars (Tier 4 ) with an initial cash of $20,000. In order to unlock more cars you would have to complete Challenges and Missions in order to proceed to the next tier. As for cash, you would just play any usual race in order to increase your total (The races in the beginning start off about $10,000 and later move towards $30,000).

For Example:

Tier 4

Nissan 240SX and etc.

Tier 3

Mazda RX-7 and etc.

Tier 2

Porsche 911 Carrera and etc.

Tier 1

Audi R8 and etc.

There are special missions after completing a portion of the map, where you would have to chase down your opponent and defeat them. In doing so, you would obtain a Pinkslip and can pick a car of your choice that is listed. Pinkslip cars hold no value, so if you sell it you won't gain anything out of it. The benefit to Pinkslip cars is that you can buy the same car without spending any money on it, so if you lose your car to the police, you can always bring a replacement to the same car. The only time you will spend money on a Pinkslip car is on performance upgrades and cosmetic upgrades, I highly go against upgrading any Pinkslip car since the unlocked cars will have more power over these.

If you wish to save as much of your money, limit your upgrades to one car until you unlock the next Tier and move on from there. As well as complete many races and challenges to improve your Driver Skills and reduce the pricing to Performance Upgrades.

The cars you buy you get to keep, there is no Pay To Win method in Undercover or any use of Real World money to buy cars. Everything in Undercover is In-Game currency.

You get pink slip cars after specific events.

Palm Harbor Rally - tier 4 pink slip car, Lotus Elise is fastest

Versus - tier 3 pink slip car - Audi TT is probably the best of the tier 3 pink slip cars

Tri City Tournament - tier 3 pink slip car - Challenger or RX7 (Audi TT is better)

4 GMAC car jobs - tier 2 pink slip car - Gallardo or GT2

Meet Carmen - tier 2 - BMW M6 (not as fast as other tier 2 cars, too late to be useful).

For tier 4, the pink slip Lotus Elise is the fastest. For tier 3, the Nissan GTR is fastest, but buying it means you'll have to wait longer to buy a tier 1 car, as you won't have enough money. For a tier 3 pink slip car, I recommend the Audi TT, since it has the best handling. For tier 2, the pink slip Gallardo or GT2 are fastest. For tier 1 there are no pink slip cars. Cars going airborne over bumps and jumps is an issue for the faster cars, and since the Zonda has the most downforce of the tier 1 cars, it's the fastest. (The CCX is a bit faster, but it's not a career car.) Also driver skills increase power more than they increase handling.

As for performance parts, you could use the Elise with race parts in the tier 3 events, but that would mean using just one car for about half of the career mode, so I recommend Elise with street parts and Audi TT with race parts (or the GTR if you're willing to wait longer to buy a tier 1 car). Pro parts get unlocked about 6 events before you get a pink slip tier 2 car, so it's not worth it to put pro parts on a tier 3 car.

Note that "current" races on the GPS map don't include races more than a few levels old, and unless you switch the mode to "available" you'll end up skipping some races because the GPS map won't show them in "current" mode.