[RyBMW]

If you're the primary and your friend is the co-signer, the bank will go after your friend if you don't pay. The loan will show up on both parties' credit report. They check the credit/income on both applicants. They do take the primary applicant's information into account more. You can have the car registered under the primary or the co-signer.

Getting approved for a lease is harder. Especially with BMWFS, it's either "Yes" or "No". Most of the time you will need to have a car loan prior to getting approved for a lease.

Also make sure your credit history is long enough. You can have excellent credit, but if your credit history is short, you can get denied for a loan also.
Can you put down a big downpayment? This will help improve the chances.

Without any documented income, it's hard to get a car loan. "How would you pay for a car loan if you don't have any income?" That's how the bank will see it. See if your friend wouldn't mind being the primary applicant. Just make sure he's not purchasing a house within a year. It might ruin his chances at getting a home loan.

I probably missed some other information.