Well, I don't have a carpet cleaning business, but my dad has his own business, I manage the office at a business, and I am studying business.
Carpet cleaning services is a competitive business. While you have competition, you must provide better quality work at cheaper/same costs. Licensing/insurance for the business may go off of the amount of profits you obtain. It may (equal) about another $70 a month (give or take a little).
I think carpet cleaning would be a great business to get into! Most households/businesses have carpet that needs cleaned. You'll encounter customers that can't clean their carpets or just don't want to; thus, they'll hire someone to do it. I would take into account that you may encounter some nasty scenarios: i.e. flea-infested carpets, carpets with feces/urine, or other dirty circumstances. If they wouldn't bother you, go for it!