What advantage would there be? If you are applying for secured cards, it is presumably due to damaged credit that you are in the process of rebuilding. The security guarantees the card, which if you had two potential applicants but with different credit quality, you might instead open an account using the name of the person with the better credit, then put the other person on as "authorized user", obtaining both the benefit of the available credit line, and placing the account history on the AU's CR, to start rebuilding their credit until they can obtain their own account. Two joint applicants are like co-signing, in that both applicants guarantee the card, redundantly with the security, yet the credit of the worst applicant might set the credit limits and terms available to both for opening the account, as well as at what point you can shift the account from secured to unsecured. I don't see what advantage joint secured account has, over single secured account with authorized user, followed by pushing toward unsecuring the first account, and getting an independent second account in the name of the authorized user, as part of an overall strategy to rebuild credit. In either case, it is more straightforward legally, and in terms of limiting risk, to not link account liability thru joint accounts.
Opt for authorized user additions to established cards. Secured cards take at least six months to garner anything more than marginal increases in FICO scores.
