I too am an "old" guy and would suggest that you get out there and do it....
I will offer some ideas next, but wanted to tell you why I say that. Life has a way of it's own, and some times it includes you, and sometimes it excludes you...in my life I have started over 6 or 7 times from nothing/nada/zero. At 18 was going to be a pro football player, was actually pretty good...until playing a pickup game and at 20 years old shattered my right knee...3rd year electrical apprenticeship down the toilet - could no longer insure me, car gone, apt gone - my mom let me move back in till I healed and learned to walk again...dad did not speak to me for almost a year.
Started a new job in computers, was great, then got typhoid traveling for work.
And so on till 2008, #7 I think...disabled at 54...nothing I did caused it, just the great karma gods saw me and said...
Anyway lost the boat we had bought and were living aboard and pretty much everything else, again.
So back to your OP.....while you are young, no real responsibilities, no kids, no drama....get out there and do it....You can offer your self as an apprentice in exchange for room and board or a small stipend...there are even give away boats in almost every place near the water.
As the others mentioned there are the normal ways of getting aboard. But were I you, and I was at that age...I would offer to crew the next marion/newport to bermuda race, transit the Panama canal as a line
handler, offer to l help a delivery ...won't pay but you will get a room and a meal, while you are learning....and you won't have $10's of thousands in student loans when you discover what you want to really do for a living.
Down sides are you may meet a girl/guy, you may get a real job offer, you may be hungry or tired or dirty....but you will be living on your own terms....just don't forget to enjoy it and don't avoid decisions to be made or doors that are opened to you....
Best of luck