Find a yacht club, like mine
Welcome To The Yacht Club of Cape St. Claire, close to where you want to sail. Send a email to the commodore (me in the above case) and see if they can hook you up with a sailor. I do this routinely, it's part of the duties and responsibilities I love most.
We 'race' fridays. It's more about sailing the course as best you can than speed demons with Mylar sails. For you, it's free.
The best way to learn to sail is free, on someone elses boat. The down side is you only learn to sail as good as the skipper/owner of that boat. The up side is you have a heck of a lot of fun and meet fellow sailors for free.
Buying a beater can have liabilities. Not just slip fees, maintenance etc - but if it's really a beater you will not be able to sell it (or even donate it, ask me how I know) - you will have to pay more to trash it (yes, cut it up and haul it off) than the boat cost.
Think it through, find and make a sailing buddy. Sailnet or local yacht clubs are a good place to start.