Here’s how these accounts (not to be confused with flexible spending accounts) work: You put aside tax-free cash that can be used only for future medical expenses, such as co-pays and over-the-counter medicine. If you have a health savings account at work, your employer might already pay any fees your account accrues. But if you open one on your own, you could be dinged with major charges for opening the account (up to $50), annual or monthly maintenance (as high as $105 a year), and even per-transaction costs (meaning you fork over as much as $4 each time you make a payment to your doctor or pharmacy), says Roy Ramthun, president of HSA Consulting Services, a consumer-health-care advisory firm. To keep your money stash from being depleted by fees, search for an account that offers the best deal based on your usage. You can open an account at any bank, including those online or out of state. Go to vimo.com/hsa to find one.