Another option is being an ASA certified instructor. Sailing instruction is often combined with renting boats.
We chartered from this company Emerald Coast Yachts - ASA Sailing School and Charter Company
a couple years ago.
What they do is find people who are willing to put there boat in charter. They take a percent of the charter revenue and the boat owner gets the rest.
It was a couple and they were working very hard but seemed to be better after a couple bad years because of Katrina.
They didn't have to own the boats.