Nope, not common at all. And the word competitor could be every other company out there. Unless every company demands to see tax returns it will be difficult to

Nope, not common at all. And the word competitor could be every other company out there. Unless every company demands to see tax returns it will be difficult to verify anything from taking after-school classes/tuitions, stock trading....may just push people to take up contract work or freelance for the most part.