Don't worry too much about the future. You'll quit going to sea when you're ready. It could be two weeks after casting off or never. One of the good things about being older is realizing what is truly not do-able and what is merely unconventional. I think you've got that down. You're not leaving a wife and three kids on the dock with $2500 to tide them over! The one thing that you can never reclaim is your youth and theopportunities it holds.
I quit going to sea, as a profession, when I woke up one day and felt it just wasn't the same and I wanted something different. Some of my classmates did that after one year, I did it after 20 years, and some of them are still out there.
Do not worry about the future, beyond say six months, as none of us know what will be. The only thing we can do is take what, for us, seems to be the correct path at the time. Most of us, at 25 years of age, had plans and ideas of where we'd be at 50. Most of us are not where we thought we'd be. I don't mean that in either a good, or bad sense, only in a sense that we are all amazed at the twists and turns our lives have taken. Things that meant everything to us 20 years ago now mean little and the things we thought little of are now the most important things in our lives. None of us are Nostradamus, and able to see the future, and all we can do is what feels right now.
Even at 50 years of age I find that most of what inhibits me is actually b.s. I can sell my house and move, I can change careers, I can do just about anything I want if my imagination is big enough and I want it. My only constaints are a wonderful wife (irrepaceable, given my personality) and 4 years of help with college expenses. Everything else is negotiable. And, you know what? The more I remember that the happier I am, because I'm not going to stay one day longer in a situation that does not fulfill my dreams. I wished someone had told me that it is ok to be frivolous and deal with "life" later when I was your age. Do you know what makes God laugh? People making plans. Think about that one. Good luck.