A government press release stated that the aim of the new rules is to prevent the legalization of illegal incomes, terrorism financing and the rapid growth of weapons of mass destruction. (coinstaker.com)
But you can not register a guy from the street who pays you (and additionally if the flat is state owned, collecting money from somebody for living there would be totally illegal income). (politics.stackexchange.com)
The fact that you have income not included in any other part of the return (illegal income goes under «other income») doesn't imply you've committed a crime — lots of people have other income. (law.stackexchange.com)