You couldn't in practical terms. The vast majority of premodern people were peasant farmers who owned no capital other than (possibly!) the land & livestock they farmed and the tools used to farm them. All this having almost no liquid value in the market such as it existed at the time. It was essentially impossible to pick up and start over somewhere else. That's aside from if you even had the right to do that; depending on time and place peasants were sometimes legally bound to their landlord.

You couldn't always just leave your village. Family, friends, livelihood was all tied there. And it's still just as difficult to up and leave.

I don't know that this was true.

I was recently reading "A Hangman's Diary", which included a Forward for the modern reader. It would appear that outsiders were viewed with extreme suspicion in those times. Obvi that's just a single snapshot of a single region, but it makes sense.

"what did this person do that they left all their family and friends to come to our town"