That really depends on geography, if you border with a rich country also the poor people can migrate illegally just by crossing the border, that's what happenin

That really depends on geography, if you border with a rich country also the poor people can migrate illegally just by crossing the border, that's what happening with Mexico and the US or Africa and Europe. But indeed those people don't always do so well in their new country, it just creates more problems. In general migration is not such a great solution because once too many people migrates from the same place it just creates a nation within a nation and you are setting the country for the next civil war, whether proper war or low key between all the different groups. The best way to solve the issue is within each country, China did much more to alleviate poverty for a huge number of people comparing to what migration achieved.