Disclaimer: *Clueless newbie alert*
As the disclaimer says, I don't know jack about long-distance cruising, but one thing I see a lot of on this forum, are people who show up thinking that they're going to sustain themselves through internet entrepenuership. Ie- blogging, Google Adsense, tech writing, writing fiction or non-fiction books, etc.
These people give me the feeling of those cheezy "Make millions working from home, on your own computer!" get-rich-quick advertisements. Yes, it's possible but you have to be really savvy, and offer something unique. I think ChrisnCate are doing this, but it's my understanding that they were engaged in this sort of employment long before they took up sailing and aren't jumping into "internet employment" blindly.
As for other means of employment, there's the visa/work permit issue that was mentioned above. It seems to me, that if you have to work to finance your long-term cruising desires, you need to have a serious, high-demand skill that you can parlay, and cruise the coasts of your home nation where work permits aren't an issue.
Diesel mechanics, sail repair, fiberglass work and sailing instruction (licensed of course) come to mind. I do know of a young couple that are successfully doing this, so I have a little insight, but not much.
S/V Old Shoes
1973 Pearson 30 #255