You picked a good time to get into the sport- there are many, many used boat bargains out there right now. A couple of thoughts- first, you're going to have to move it. What are your towing capabilities? You probably don't want to invest in a $30K truck and a boat at the same time so your ability to move it will have some bearing. For new boaters, I always try to recomment a reasonably new 24' to 28' deep vee with a single big block. Baja makes a great first boat. Fountain does too but you'll spend a little more. One of two things will happen- you'll either love the sport or you won't. Either way, you'll be looking to part with whatever you end up buying in a year or two. You will want a recognized brand that's easy to resell or for a dealer to take in trade. On boats- condition is everything. Lots of people think they'll get something 20 years old for low bucks and fix it up. Thet's a great way to make a pile of cash disappear. A 20-year-old boat you pay $10 grand for ans put another 10 into isn't a $20K boat- not even close. Many people use their boats right up to that point where they still look and run OK but major work is right around the corner. if you're going to drop $20K, you might as well have a boat that's at least close to worth that much.
For any of us to make a decent recommendation, we'll need to know how you'll use it and more on what your expectations are. As far as the offshore running you reference, that's something you're probably a few years away from. Open ocean boating can be great fun but it can also be incredibly perilous and is only for an experienced operator. You're also going to need alot of boat on all but the best days. Go buy a book called Chapman's Seamanship and start reading.