My thought process, which will in the end result with a question, started from the book History of the Portuguese Empire (which i read a longer time ago) where some by the way remarks implied a connection between 15t-16th migration of non-christian/catholic population to and from Portugal (in particular Jews, others also) and the increase/decrease in economical and technological prosperity of areas in the time.

The narration, as I formed it, was something like this: In the early ages of Portuguese exploration, Muslim and Jewish scholars, scientists, cartographers, thinkers (and i guess business men?) were accepted and invited to help the Portuguese in their quest. Later (and by that time Portuguese already had sort of monopoly in the Indian ocean) pressure begin to mount (internal and from Spain) to deal with "infidels". Non-christians were through stages forcedly baptized, prosecuted and ultimately they fled or were expelled. Again according to my summation, a large number fled to Antwerpen to join a base of their Jewish relatives/friends already there. Soon Antwerpen sprouted into a large business hub. E.g. while Portugal was the main supplier of spices, the Portuguese ships supposedly went straight to Antwerpen to sell their cargo there as that was the main spice market. Then a event in a war (Dutch revolution related I guess?) caused all non-catholics to be expelled from Antwerpen and the trade population again, as i gather at least, moved to Amsterdam, which then became the main center of commerce.

Okay here I think it is quite possible I have a case of cause-effect error and am forgetting a myriad of other circumstances that are sure to had played a large role, but still, this thought intrigued me, together with today's reality of inter-European work migration, expating and such.

I know at the time it was normal to have mercenaries from foreign countries going around working anywhere. Ships also employed high percentage of foreign sailors. And we have micro-scale cases of people moving around: Columbus was a Genoese captain (the most accepted thesis of course. I am looking at you Spaniards) who worked for Portugal and Spain, and was certainly not the only one. Leonardo Da Vinci switched city-states in Italy depending on patrons. Gutneberg was also moving around if I recall correctly. Etc. a lot of examples in all parts of Europe can be found.

Any comment on the validity of the above statements is encouraged, but it is not my direct question. I am more interested in the general migrations (work related mostly) of the period.

Was there a something of a "common happening of work-related migration" then, or was it just a few notable examples? Did it have such a great effect as my above statements suggest? Is there a case in that period where for example a city/state opened it's doors, and skilled men arrived and the area blossomed? Or if an area was poor, that a lot of people moved away from it to some other areas in a large scale? I heard Low Countries were very popular to immigrate into around that time?

Also an important question: was the scale of the migration something unique for Europe (or parts of it anyway), or was it normal practice everywhere in the world?

Also the formalities? Could a person then just move to another country/city without much hassle? Did they have "visas" and "work permits" or could they just come and look for job anywhere? Both high skilled scholars, but also workers and laborers? Was there control, inspection, and was there some sort of resentment for "immigrants"? Was it different for Christians and Jews / Muslims? I am just guessing Jews moved a lot with relatively common prosecutions, but did their movement have some sort of positive or negative correlation to business growth and economic prosperity?