"Yes but..."
Anyone <18 can't usually obtain credit. You could have a joint savings/invedtment account, however.
Real problem is this: what if one of you draws money out? Bank unlikely to demand 2 signatures. Even if you cohabit without benefit of wedlock, it's a danger.
Instead, why not have 3 accounts: one yours, one his, and savings account joint but only for payments into household expenses budget. Salaries go into an individual's own account, you jointly decide what household expenses should total each month, and each of you has a standing order (own acct to joint acct) for half of total. The joint acct would then be empty just before paydays, so no risk of one of you running off with other's hard-earned savings.