If you live near a lake or big river and love being on boats, why not consider buying a used steamboat and giving scenic trips to tourists? This is a line of business that takes a little planning and the right license, but it's unique and lucrative. A ninety-minute steamboat ride goes for around $15 for adults, and $10 for children 6 to 12; children 5 and under ride free in most cases.
Steamboats are designed to carry between 50 and 150 passengers, so you can see how much money you can make in a single day running as few as four tours. Many steamboat operators also offer luncheon and dinner cruises; I've seen those advertised at $27.95 and $45, respectively. This is a popular attraction anywhere there's a good-sized body of water.