Can the government strip illegal aliens of their material wealth?

Probably. Cities can take away anything a person owns if they say it was gotten illegally, like from selling drugs - I do not think that is right. That also takes away everything from any spouse and children.

It probably differs depending on where in the world you are.

Why not. It gets away with anything it wants to.

Yes, because being flush with illegal cash, is why these folks choose to clean your toilets.

In the US they often do.