If you haven't read James Baldwin's site yet, do so.
Atom Voyages | Voyaging Around the World on the Sailboat Atom
He also has compiled a list of boats he might recommend.
Atom Voyages | Voyages Aboard the Sailboat Atom -* Good Old Boats List - choosing a* small voyaging sailboat
Many are older designs that can be had for fairly little. You *will* have to be prepared to do the work yourself! For <$20K there is really no other option if you want a safe boat for passage-making.
Your biggest problem right now is probably that you are at the ponit where you don't know what you don't know. Now...this was your first post. How much sailing experience do you even have? Your best bet is to forget about "Bahamas and beyond!" for a few seasons. Instead you and your friend should focus on learning to sail the coast of Florida. Cruise together for a week at a time in local waters and see if it is even something you both can handle. A boat is a pretty cramped space. Living together in a 30' fibreglass bathtub can cause quite a bit of friction. Especially when you are both exhausted, the weather is crap, and nerves are frayed. Better to discover that before you are several hundred nm offshore.
The suggestion to crew someone else's boat is also excellent. You learn important skills, still go where you want. At the end if you find the lifestyle isn't for you, you at least don't have a boat to sell. If you do enjoy it, you have a much better idea of what to look for in a boat.