sazor
It's easier for some professions as they have more mobility and skills are transferable. But I've seen people from all sorts of backgrounds.
There are some folks involved into crypto/gambling/other questionable companies but I would say they're minority and rarely move to EU/UK/US because of regulations and taxes.
I'm not from an even remotely wealthy family, not a mafia and was able to move to the EU. Not exceptional by any means.
Other than that it was quite good and on schedule. I’ve used railpass so it was also cheap enough.
My longest voyage was Moscow-London back in the days when Moscow-Berlin and Moscow-Paris trains existed (pre-covid).
Last summer Spain’s Renfe offered huge discount for a pass for people under 31. Only for paper version though which is slightly less convenient but worth it anyway. I guess other eu countries could have similar seasonal discounts.
It does miss some regional train tickets which could be found on local platforms but major lines are covered fine.
Also, capital gains outside of Spain sourced income are not taxed in Spain.
Social security contributions are paid in full same as usual tax residents.
Tax treaty doesn’t apply for such tax residents though and it complicates taxes in general.