The way you asked the question makes it sound like you haven't done DIY body repair work before. It's not really difficult stuff to learn, and the basic repair materials are not expensive. However, it can be messy and time-consuming work, depending on the amount and quality of repair you're looking for.

That said, it's difficult to halt rust completely, once it's in progress. You can keep patching, but eventually the frame or other safety-related component will be compromised, and extensive replacement is likely to be required at that point. But, you may be able to keep it on the road for a few more years, if you're willing to put the time and effort into it. Don't bother asking a body shop, because their estimate would be more than your vehicle is worth.