I live near the Dutch border. I know quite some people from a "Kamper" background. Some of them moved from their trailer parks in the Netherlands to Belgian border towns, where they bought up cafes and other small businesses. A few also work out at my gym. To say they're all criminals, is not true. But I dare say that all of them at least have family that's involved in organized crime; ranging from the manufacturing, importation and distribution of drugs (a lot of marijuana grow houses for instance have some involvement by them), gunrunning, stolen car trafficking, illegal gambling, owning brothels (which they rent out to foreign pimps)...

Anyways, they're an entirely different breed from the Eastern European Roma gypsies. They're 100% ethnically Dutch, although a certain amount of them can also trace their roots to the Alsace and Eifel regions. There are some that live in mansion-like mobile homes, but that isn't the standard for all of them. And generally they highly dislike the Romani gypsies from Romania, Bulgaria...

I don't know what the behavior of the American trailer trash is like, but the Dutch ones won't really bother you unless you come at them. Some time ago I talked with a few of them at a heavy metal show (Crowbar) in Tilburg and they were quite amicable.