Cheating Uncle Sam

Question

I was wondering what the Rav thinks about people who: 1) Earn part or all of their money "off the books", and therefore pay less taxes and may be eligible to receive government assistance for which they would not otherwise be eligible? 2) Arrange their affairs in such a way as to receive maximum government assistance, for example, having someone else's name on the title to their house, so that they are nominally a renter and thus eligible for HUD? 3) What about someone who is aware of such activities, are they obligated to inform or forbidden to inform? 4) Does it matter if the persons engaged in 1) and 2) above are busy learning or teaching Torah (ostensibly)? Thank you very much for answering this question as well as running this website.