My .02 cents worth (and well worth it!)...
Sail repair...not enough need for this to keep the $ rolling in. Many boats have sewing machines, or know someone who does. Free repair is the norm, not the exception.
...we are talking about an almost endless combination of variables here. Multiple sizes of multiply-inter-connected complex systems mounted in multiple ways...each system with multiple points of failure. Lots of multiples. My point is, unless you have been a mechanic for a lifetime, and have it "in your blood", taking a few classes
will not prepare you to realistically address the issues you will be asked to fix. Yes, some people can do it, but they are the savants of the mechanics' world. And carrying the parts
supplies necessary is a daunting, and very expensive (and heavy) proposition.
My (almost) serious advise...buy an ice maker. People will flock to your boat for happy hour. They will bring food
, so you don't need to buy any. A penny saved...