I don't know whether these types of training programs still exist, but in the past investment banks would have extensive training programs that rotated trainees through different departments. This would give extensive experience in the issuance and creation of debt and equity securities. I've heard of some banks, Chase in a particular case I think that did a similar rotation through different departments, but more on the retail side with banking, investments, and loans.
You could also take a job as a financial advisor trainee. You'd study for at least the securities license exams, and depending on the firm you chose, also possibly insurance licensing exams. The exams are fairly poorly written and the study materials sometimes more so. They do not reflect reality very closely. But you would still get a greater background in finance than without studying for and passing them. Your on the job training, depending on the firm, would likely be the most valuable part of learning finance.
All that said you definitely do not need to get a job in finance to learn finance extensively. There are plenty of options from self study, college courses, seminars, community education classes, and possibly free MOOCs where you can learn finance to almost any level of depth you like.
