Exactly. Actually many people in trade jobs (construction, hairdressers, etc) additionally work in illegal employment (or do paid "favors" for acquaintances), a

Exactly. Actually many people in trade jobs (construction, hairdressers, etc) additionally work in illegal employment (or do paid "favors" for acquaintances), at least speaking from my experience as a German in Germany. This usually has to do with those jobs being too badly paid to attract enough people to do all the available work as well as those jobs not paying a sufficiently livable wage and welfare being tied to unemployment or fully deducting any income 1-to-1. A naive solution would be converting welfare to something of a reverse income tax (so e.g. for every €2 you earn your welfare would be reduced by €1 rather than €2, down to zero, and no income tax would be paid on any income up to 2x of welfare). But politicians seem to be more interested in squeezing welfare recipients harder because they think people who aren't working (legally) must be punished until they start working - nevermind that some of those welfare recipients are not part of the work force due to age or legal status and thus can't legally work.