When I sailed, there was no internet, so I managed a couple of ways. First off, I didn’t have many bills. I had a car (kind of a beater, but it ran) that was paid for, lived in an apartment. My bills were monthly. For awhile, I paid while I was home and sent the rest in when at sea, from US ports. Every once and awhile a payment would be late, but not very often. Eventually, I had a friend, female, who wasn’t my girlfriend pay my bills. I set up a separate joint account and kept it with enough bucks to pay my bills. It probably wouldn’t have worked if we were more than friends; but I never had a problem. When I moved from that town to south Florida, I went back to just paying my bills either at home, or while at sea, from US ports. Eventually, I got married and passed all the duties off to her. Even when I came ashore, I saw no reason to take the payment duties back from her. She did a pretty good job (other than running up the credit cards) up until we got divorced, and then I had to figure it out all over again.
Life at sea is much different now as you can see from other threads (I hesitate from saying “better” since I kind of liked the isolation), with communication fairly easy. No marine operator calls (although those were fun to monitor), no telexes, etc. I often thought about living in DR or some other places, but never did. I did run across one of my college classmates that was sailing 2nd on a Lykes Brother ship back in the early 90s who was living in Thailand. He may have screwed the pooch, though. He had a steady girlfriend (wive?) and they owned a ranch.
It is a different lifestyle and not many can make it work. I enjoyed it, but came ashore for other reasons. It helps now when I have to take off for an assignment, sometimes at the last minute, and be away for either a few days, or a couple of weeks.