I one time left white lines on an off-white wool rug after using my steam vapor machine on it, with the intention to destroy any dust mite allergen in the rug. I ended up taking the rug to an immersion cleaning plant. They ran it thru their system three times. The customer was satisfied that the white lines had been removed. That has been my only experience of this type.
Do you have a portable machine you could HWE? If you do I'd try cleaning it with that first, probably just a cold water rinse.
You might want to think about using a porty to clean those rugs and finding a cleaner who will clean rugs at a discounted rate. You could be passing up profits if your cleaning the on the cheap in custys home.
You should be able to find a rug plant operator willing to work with you in this way. I would make it part of the deal that HE is the party to pick up the rug/s at the customers home or business, and to return them as well. Otherwise you will find yourself frequently wrestling alone with large rugs
that may not even fit into your work vehicle. Let the rug plant people do all the heavy lifting AND the cleaning, and agree to a reasonable referral fee.