1. You don't say what the boat is. If there are a sizeable population of them, you could race "one-design" against identical boats. If not, you can race "handicap" in the PHRF fleets. Your boat will be assigned a handicap rating based on it's hull and rigging measurements. There are categories of racing (4P, 5P, 6P) which describe the level of equipage and construction that your boat must comply with in order to race in certain venues (creeks and rivers, bays, off-shore, etc)
2. There are single-handed races, but you'll be able to participate in more races if you can scrounge up at least one crew member.
3. Usually, there are paper clubs and sailing associations that have no club house, and very minimal dues that you can join, so that you can participate in most racing in your area.
4. No. Almost all racing is for trophies and bragging rights. Any money made is usually for charity and never touches your hands. If you're racing to get rich, find another sport, like NASCAR.