Re: Very n00b questions from a prospective sailor.
Hi and welcome to Sailnet.
Sailing lessons aren't generally cheap, but in my opinion they are worth it. It's nice to get some experience under your belt before buying a sailboat of your own. Also, renting boats or joining a sailing club is generally a much cheaper way to get into sailing than purchasing a boat.
You don't mention what $500 will buy, but generally $400-$650 will cover a weekend sailing course. An ASA certification course is usually longer and more expensive ($900-$2000). Hopefully someone in your area will weigh in this thread with recommendations for schools and clubs.
With regards to slip costs - there's enormous range here. In the Chesapeake region, costs range from $1000 a year for bare bones marinas to $5000 for country-club style marinas. In between, expect to pay about $2500-$3500 a year for a slip in a decent marina with some facilities (bathroom, pool, maintenance yard, power hookups). Moorings are cheaper but you need a plan for getting to the boat (and a place to store a dinghy) and for working on the boat. NY/NJ prices might be even higher than this.
Good luck and welcome to sailing. Not the cheapest sport on earth, but so much fun.
1987 Pearson 28-2, Deale MD