Re: how much experience do I need
I asked a similar question to an experienced friend when first getting into sailing. I was asking about sailing from Seattle upside the inside passage.
His recommendation was about 150-200 hours of sailing experience in a variety of conditions. I probably got about 300 hours of experience before doing the trip and felt like that was a good amount. Another way of putting it is a year of sailing multiple times per week and with some shakedown multiday trips.
15,000 is a difficult amount to have for a reliable boat. If you are staying in protected waters that will easily get you a 25-27' boat and leave you with enough money to replace equipment to get it into a good sailing shape. If you want to go offshore you'll already need to be an experienced sailor who is good at working on boats to identify the right 15,000 boat to buy. They are certainly out there, but 9 out of 10 boats listed for that amount or less will need a significant amount of money invested in them to sail safely offshore.
boats that I sail on regularly: Pearson 28-2, Rondar 505, Yankee 30, Blanchard Junior