You start off with one race unlocked. As you win, the next race gets unlocked. Win them all in the series and the car is yours.
C/D class Saleens
If you have not bought a Ford Mustang GT Coupe and a Ford Mustang GT Convertible, do so. Take them to the U.S. Muscle Car Tuner shop. When you get there they will ask whether you want them tuned as a Ford or a Saleen. Press Down and select "Saleen". The new car(s) will have a very visible sign that says "Saleen" at the top of the windshield. They will also be upgraded to C/D class cars.
Easy Master Points
To get easy master points,you can either 1.Drive behind another racer to do slipstream or 2.Get a fast car(I used the Koenigsegg CCR) and drive on the highway for as long as you like, the points will come faster if you drive faster.
Easy money
Go to the bottom of the map by the crater. There is a speed challenge there that awards $40,000. A C-Class car is required (TVR Sagaris recommended). You can do it in about 1:30 to 2 minutes and get $40,000, which results in about $1,200,000 after one hour.
More money
Find the highway and go to a spot near but not too close to an intersection. Find a racer and get them to have a Instant Challenge with you.. Set the finish line just behind the start line on the opposite side of the highway. Once the race starts immediately turn over the center of the highway and drive past the finish line. Do this five or ten times then do a race that is worth about $20,000. You will get a lot of money for the win. Note: This does not always work.
Own all houses on the Island
Race and get gold in all these races and you will earn all the houses.
Recieve free cars
Become president in these car clubs to have the corresponding cars get sent to your garage.
Effect - Code
Caterham CSR 260 - President of Clubman Car Club
Chevrolet Corvette Stingray 69 - President of Classic Car Club
Ford Shelby Cobra Concept - President of Club Stripe
Jaguar Type E coupe - President of Club d'Elegance
Lamboghini Countach 25th Anniversary - Earn 1,000,000 points
Mercedes-Benz CLK DTM AMG - President of German Car Club
Shelby Cobra Daytona Coupe - Earn 500,000 points
Spyker C8 Spyder T - President of Accolade Ala Moana Club
Recommended cars for each class
This following is a list of the best overall cars and bikes per class. Note: This is assuming you have the best performance kit for each vehicle without bringing it out of its class (mostly level 3). Note: The first vehicle to appear is the best of the class overall. Others, such as the CC8S in A-class might be a better choice for long, straightforward courses. For the MA-class, the MV Agusta is better in all stats than the Kawasaki, but some prefer it because it is much cheaper than the MV Agusta and also because of its first gear being longer.
G-class
Shelby Cobra Daytona Coupe (Amazing top speed, acceleration, and handling for its class, but has to be unlocked first; has stats similar to C or B car)
Lamborghini Muira P400SV (good top speed, 198 mph)
Aston Martin DB4 GT Zagato (good handling and lack of drift; costs $3,000,000; level 3 kit $80,000)
Lamborghini Gallardo Spyder (best for handling, 94%)
Noble M14 (best for top speed, 208mph)
B-class
Ford GT (best for acceleration and braking power; same top speed as Dodge Viper SRT-10)
Dodge Viper SRT-10 (slightly better handling than Ford GT)
Farboud Supercharged GTS Prototype 2005 and Jaguar XJ220 (best for top speed)
A-class
Saleen S7 Twin-Turbo (best for acceleration 93%; and great top speed 250mph)
Koenigsegg CC8S (best for extremely high speed, 263+ mph)
Enzo Ferrari (best for handling, 100% from the start; braking, acceleration, 90%; and lack of drift)
MB-bikes
MV Agusta F4 Brutale 910S (best for top speed)
Kawasaki Z1000 (best for acceleration)
MA-bikes
MV Agusta F4 Tamburini (best for top speed, 220 mph without drafting; handling, 100%; acceleration, 93%; braking power. 96%; and lack of drift; $45,000; level 3 kit $40,000)
Kawasaki Ninja ZX-10R (has same handling as MV Agusta, but top speed, braking power, and acceleration are worse; $14,000; level 3 kit $25,000)
Teleport to any road in Oahu
Finish all the King of the Hill races on the island.
Unlockables
Effect - Code
Alfa Romeo 8c Competizione - Win the Tour of the Island race.
All Challenges - Reach the "Champion" rank.
Bike dealerships - Go to all the car showrooms on the island.
Chronopack - Buy your second vehicle.
Chrysler Firepower Concept car - Complete all the Courier driving missions.
Chrysler ME Four-Twelve - Win all the Race challenges with a "Gold" rank.
Editor mode - Reach the "Pro" rank.
Ford Island - Reach the "Expert" rank.
Ford Mustang GT-R Concept - Complete all the Vehicle Transport driving missions.
Ford Shelby Cobra Concept - Complete all the Top Model driving missions.
Ford Shelby GR-1 Concept - Complete all the Speed challenges with a "Gold" rank.
May the Best Man Win - Reach the "Champion" rank.
Oahu Raceway - Reach the "Pro" rank.
Paint shops - Get a "Gold" rank on the Around the Crater race.
Photo mode - Reach the "Amateur" rank.
The Legendary Record - Reach the "Champion" rank.
The Reward - Reach the "Expert" rank.
Tuner shops - Reach the "Amateur" rank.
Volkswagen W12 Coupe - Complete all the Time challenges with a "Gold" rank.
Volkswagen W12 Roadster - Complete all the Hitch-Hiker driving missions.
Walmaealamae Haven of Peace - Discover all roads on the island to get this house.