I am assuming that many that want to immigrate from countries in Africa or other 3rd world countries- would like to be able to work, live in a nice house.
And this leads us to the final piece of the puzzle. Why do you think Africa is in such disarray? How is it that there are so many valuable resources contained in a continent so well positioned in the world and yet the people who inhabit that continent are completely unable to harness those resources without a war breaking out?
One possible answer is that Africans just don't know how to build nor function in society as we know it. If that is the case then keep the doors closed when they come knocking and knock em down if they come in. But could they really be so utterly dysfunctional within a modern society?
Another answer is that Western influence/disturbance/manipulation is ensuring they never form effective communities and certainly never harvest to their maximum potential the resources they were born into. Who's benefiting from that? You? Me? No, there are a select few who benefit from this and it's not them that has to worry about: disjointed communities; increases in violent crime; increases in drug trafficking; rubbish strewn across the streets when these people move in; affirmative action (and other idiotic social policies that pop up as a result); slum lords and other predatory renters.
Who does have to deal with that? You. Me.
If I'm wrong then I'd like to know why Africa is a dump, why India is a dump and why the Middle East is a dump?