Let's organize this differently.
1) Either you're going to sell goods (including intellectual property) or services.
2) Your clients are either to be here or there (home or abroad).
3)
Income is going to be generated a) pre-cruise, 2) cruising, or c) post-cruise.
Sell Goods at Home Pre-Cruise - This is probably your
current day job; but there may be a domestic market of pre-cruisers for novel ideas you patented or copyrighted while getting your vessel ready to
cruise. If you had a novel idea and haven't yet protected it, then beware of marketing it too soon. Of course, these items will have greater value post-cruise when you can say they are field-proven.
Sell Goods Abroad Pre-Cruise - Contact all
marinas, yacht clubs, chambers of commerce, etc. along your preferred
route and asked them what they want you to bring. You'll need Letters of Credit, export licenses, etc., not to mention competitive pricing on useful
equipment small enough to carry on your yacht (think diamonds). Note that it may be preferable to arrange
shipping separately so that you don't have to carry goods the whole trip, but that turns this idea into simply another import/export business. As far as that goes, while you are talking the
marinas, yacht clubs, chambers of commerce, ask them what you can sell them TODAY. Of course, if they say yes often, then it may be harder to cut the strings to go sailing.
Sell Services at Home Pre-Cruise: Again, this is probably your
current day job; but if you can find domestic companies that would pay you to introduce their goods and services along your
route - sort of a "company ambassador at-large" - then you may get "sponsorship." Your best bet would be to work with the marine equipment manufacturers/suppliers that you selected to outfit your yacht, and get the necessary training to intelligently and convincingly represent them at boat shows and other industry activities occurring within the time frame as your visit at various locales. They will probably require you to sign a
contract that severely limits your debauchery. Another
service you could pre-sell might be "Intelligence Reports" in various locales along your route - sell a select group of clients your market and trend analysis/intelligence newsletter as you travel. These would probably sell better if you already do this sort of thing.
Sell Services Abroad Pre-Cruise: Tough to do without being there.
------------
Sell Goods at Home Cruising - Photograph and write articles to publish back home. These generally fall into the "sailing adventure" or "travel guide" niches, but could potentially find their way into the international news if related to a disaster (keep the cell
camera phone handy). Alternately, buy foreign goods and export them to the USA. This generally falls into the textiles and fetishes niche, but you might want to climb the ladder of getting a local medicinal herb FDA-approved. And if you do find a local medicinal herb, then you might consider trying to de-code its DNA and
copyright it
for sale to a pharmaco. Of course, there is always the local fisherman who wants to sell
fish to your favorite restaurant back home but who needs help with the
refrigeration part - or arranging airfreight for the chef's "just caught" menu.
Sell Goods Abroad Cruising - You can either sell inventory you brought with you (uncomfortable unless small - think diamonds), sell inventory to be delivered here from elsewhere (think company ambassador/sponsorship arranged pre-cruise as above, or a business representation agreement negotiated underway at one or more of your
ports of call), or sell goods from there to elsewhere (this is probably too complicated to attempt without
legal standing in one or the other jurisdictions - but weapons dealers do it all the time). In any case, it means actively contacting all marinas, yacht clubs, chambers of commerce, etc. along your route to build relationships, and to attempt little projects together to build confidence in each others' abilities to actually perform as advertised. Be sensitive to cultural differences - I was once told that foreign corrupt practices are common, and that they are illegal in the USA (as in most 1st world countries) and can result in jail time. I was also told that in many cultures, the definition of corruption is when the Big Man doesn't create a "trickle down" effect for all his underlings, who have underlings, ad infinitum.
Sell Services at Home Cruising: These business opportunities are all better pre-sold (see above) as it is difficult to get someone to pay you without ever having met you.
Sell Services Abroad Cruising: These can range from consulting in your field of expertise to manual labor; although medicine, law, and engineering may require licenses. Others have commented that cruisers usually barter services among themselves so that community is probably not the most primed to generate cash flow. Certainly though, there are firms abroad who already market to your home base (or attempted once and failed) and could use assistance optimizing that effort. There are local manufacturers who would be interested in how to increase their exports (this may lead to exporting goods home, see above). Teach
English or your native language. Teach seamanship. Teach
music, environmentalism (pollution prevention, waste management, energy conservation), computer troubleshooting and repair, water-well drilling, etc.
-----------
Sell Goods at Home Post-Cruise - If you established business relationships/agreements cruising, then they mature into this category on return - importing instead of exporting. Other ideas include: Manufacture the gizmo you invented underway. Cannibalize your boat and sell the
parts. Collect into a retrospective your photographs and journal entries to publish, or write and publish a novel inspired by your travels. Open a restaurant featuring a "world
food basket" cuisine.
Sell Goods Abroad Post-Cruise - Again, you can either export inventory at home (your new patented gizmo), help someone else export abroad (based on the business representation agreement you negotiated underway, right?). See above for caveats about foreign corrupt practices.
Sell Services at Home Post-Cruise: Leverage you hard won knowledge to assist others seeking the dream. Teach seamanship, open/buy/or get hired by a yacht
maintenance business, sell yachts,
survey yachts, deliver yachts,
charter yachts, etc. There is always the foreign bride
service.
Sell Services Abroad Post-Cruise: Be a manufacturers representative (based on a trusting relationship cultivated cruising) to open or widen world markets. Leverage the knowledge you gained along the way of "local" markets, fashions and trends to help foreign manufacturers better sell into those local markets. Open an internet exchange to facilitate the
buying, selling, and bartering of goods and services - or work with Cruisers Forum to morph into the next generation of CF.
Whew! I'm dry on ideas - wait a minute and I'll think of some more.