If you have enough money you can buy your way into any country.
I think it's already too late for that.
[1] http://super-economy.blogspot.com/2013/05/malmo-case-study-i...
That's not what the data really says. Think, how does the SCB know if people are working? Do they follow them around? No, they only know what people tell them. So what that data shows is that less than the majority of foreign born adults declare that they're working. Now I'm sure you can think of a few reasons why a poor immigrant would have to not declare that s/he's working.
I try and tell people, I'm a skilled software developer, what Germany needs right now. And when was the last time a Canadian showed up in Europe and started causing a problem? Immigration is tiered based firstly on country of origin and wealth, not on skills.
I find it a little bit offensive that EU residency is just one more thing the wealthy can now buy. But on the other hand it was inevitable and was already largely the case. For less than $650k if you have a good immigration lawyer.
Well, you could also be living in Pakistan or Somalia and apply for asylum which most likely will be granted to you with no money involved.
If you'll read up on currency theory, you'll find some people have proposed pretty much exactly this (Jane Jacobs comes to mind, probably in Cities and the Wealth of Nations, it's been a few decades since I've last read it).
More generally: with a sovereign currency, a country controls both its monetary and fiscal policy, and can make its own allocation decisions with both. Which means it can set monetary policy to benefit its industrial / manufacturing or other economic centers, and use fiscal policy to create wealth transfers to underdeveloped regions. This is effectively what happens in the United States, for example, through SSI, welfare, medicare, SNAP, and similar programs.
In the EU, you have a bifurcation of monetary policy (ECB) and fiscal policy (independent European states). This was pointed out by numerous early critics of the EMU, including rather notably Margaret Thatcher, in the late 1970s / early 1980s. Her comments then proved exceptionally prophetic.