You ask: "How is one supposed to be able to tell if a vessel can travel the ocean?"
If you are totally "green" (as you say you are), you do exactly what you've now done: You ask a bunch of people who have already "seen the elephant".
Then you pay heed to what they tell you :-)!!
When we get enquiries like yours, the one set out in your opening post, warning flares pop off all over the place because a landsman, should he succeed in doing what you are proposing to do, would be a SERIOUS danger
not only to himself and his family
but also to other mariners.
YOUR task, now, if you would persist in your dream, is to begin to learn. As you have :-)! The people who have answered your opening post are people with practical experience, and already in possession of the necessary intellectual ballast. You can learn about the practicalities from them. But the theoretical, intellectual ballast necessary you must garner by STUDYING. Long and hard. For the rest of your life. Unless you can enroll in a marine
It is my impression, and forgive me if I'm wrong in your case, that the desire to "run away to sea" is usually prompted by some adversity encountered ashore. It is my personal opinion, derived entirely from observation of others for I haven't had the experience myself, that you cannot learn to live happily in an environment
inimical to man - as the ocean environment
is - unless and until you've learnt to deal with whatever adversity afflicts you ashore.
There are two kinds of ships: Those driven by wind
and those driven by infernal combustion engines. The only thing they have in common, really, is that they float. The concerns of "rag wavers" are sufficiently different from those of "stink potters" that we have a companion forum called "Trawler Forum" focusing particularly on the concerns of those we rag wavers consider "on the dark side". You will find it here:
After some time, a year or two, of assimilating thoughts from both forums
and reading as many books
about seafaring as you possibly can, you will (probably) become "able to tell if a vessel can travel the ocean" and you will (probably) come to realize that for crossing big waters a sailboat is the only sensible choice unless you can afford to buy, to keep and to operate what amounts to a small cruise ship
. And if you could do that, you'd just hire a professional skipper
As the Irish are reputed to say: "May the wind
be at your back"!