I can only offer my suggestions as a consumer based on what I look for in a carpet cleaning business.
-Natural ingredients only. No chemicals, and nothing that will leave a residue.
-Steam/low water cleaning, not something that will take 2 days to dry with fans.
I would think there would be a demand for it, especially if most carpet cleaners in your area use chemicals or lots of water and you decide to go with a "natural" business.
It may be challenging to start out, but since your husband is only looking for part time work right now, it would probably work out perfect! Overhead costs would be minimal as long as he gets a good quality van/truck (whatever they use!) and equipment. He could maybe offer referral bonuses such as have 2 people book appointments at the same time and get a free rug cleaning (or sofa, or extra room), or a free extra room cleaning or furniture cleaning for referring 1 person, or offer a 3 room bundle for $XX., etc.
I think it is a great idea! I don't know how much decent equipment would cost, but I would say it is a pretty low-risk business to start.
