Professional mode:
Select arcade mode, then highlight the "Hard" selection on the difficulty selection screen. Hold L1 + R1 until it changes to "Professional".

Corvette C5R
Simply beat 50% of the simulation game and you'll be given a Corvette C5R.

Team ORECA Dodge Viper GTSR
Win all Golds in the Amateur League.

Dodge Viper
To get a free Dodge Viper team Orca, beat all the courses in the amiture league.

Gran Turismo All-Stars prize (Amateur League)
Win the Gran Turismo All-Stars in the Amateur League to unlock the Mine's GT-R-N1 V-spec and Raybrig NSX.

Toyota Sprinter Truendo GT-Apex:
Successfully complete the Sunday Cup with gold medals in all three races to unlock the Toyota Sprinter Truendo GT-Apex.

Mazda Eunos Roadster:
Successfully complete the Cupman Cup with gold medals in all three races to unlock the Mazda Eunos Roadster.

Mazda Roadster RS:
Successfully complete the Spider and Roadster cups with gold medals in all races to unlock the Mazda Roadster RS.

Nissan Silvia K's 1800cc:
Win the Beginner FR Challenge series to unlock the Nissan Silvia K's 1800cc.

Silver Honda CRX Del Sol SiR:
Win the Beginner Race of NA Sports series to unlock Silver Honda CRX Del Sol SiR.

Bonus tracks:
Successfully complete each tier of tracks in arcade mode on any difficulty setting to unlock the next tier of tracks:

Tier 1:
Super Speedway, Midfield Raceway, Smokey Mountain, Swiss Alps, Trial Mountain, Midfield Raceway II.

Tier 2:
Smokey Mountain II, Tokyo R246, Grand Valley Speedway, Laguna Seca Raceway, Rome Circuit, Tahiti Circuit.

Tier 3:
Swiss Alps II, Trial Mountain II, Deep Forest Raceway II, Special Stage Route 5, Seattle Circuit, Test Course

Get Cash
After winning amatuer NA race save to memory card two then go back to the amatuer NA then save to memory card one then dont spend money.

Motorbike
L1, R1, R3 (push right analogue stick in), R2 THEN X, X, Triangle. Do this at car selection screen in arcade

Easy Money
A good way to get money is to buy an R-Type Integra and play on the R-Type series race in Beginner mode. It's really easy if you upgrade the car as much as possible. You get 5000 per race and 10000 at the end, 35000 already, then at the end you get an acura, which you can sell for 75000. 110000 in about 20 mins