I have been feverishly researching how to piggyback on someone's credit card account to benefit from their account history and show their account on my own credit report.
It seemed I had hit a dead since no applications actually allow you to add a co-applicant or joint user. So I found this article
about what credit card issuers allow co-signers.
Chase is one of the "Yes" issuers. Apparently the primary just has to call, they will take the joint cardholder's name and then mail a form which must be filled out and mailed back to Chase. My girlfriend has a Chase Freedom card and we just did it today. This makes me liable for paying the balance and obviously it will report on my credit.
This just sort of an FYI for anybody who is looking to do the same thing
Apparently Bank of America will let you add a co-signer to any account also.