I will show you how to send a car to a friend or just copie the car.
you can also buy a car without losing your money used for the puchase !!
Step 1: Copy Your Save File
1. Go To Game > Saved Data Utility
2. Select the GT5 Save File
4. Select Copy
5. Copy to USB-Stick
Step 2: Sending the Car
1. Run GT5
2. Go to 'Garage'
3. pres triangle at the car you would like to send to a friend
4. choose 'Give to a friend'
5. select the friend who would like to have the car
6. your car will be gone
Step 3: Getting Your Car Back
1. exit GT5
2. After you sent the car your savefile will have been adapted, you have to remove this save file.
3. go to your USB-Stick and copie the earlier save file to your account.
4. Start GT5 again and you will see you'll still have your car but your friend will still receave his car.
instead of using an USB-Stick you can also make a second user for you ps3 and copie the file at this account.
ofcouse you can create a second PSN-accound and send the car to your second account, afterwards you can send the car back to your main account.
At this way you can also buy a car (you'll still need enough money) sent it to a friend and if you follow the previous steps you wont lose your money.