Mike
There is " a market " for cleaning / restoring / maintaining, just about anything and I would never suggest otherwise, but, to give inexperienced people the impression, they can make money from a specialist market, by not being prepared, or capable of doing the work, to the highest standard, is IMO, misleading, to say the least.
Can't be bothered with the scoring points, which has crept into recent posts. I try to write, from experience in this industry and elsewhere.
I've cleaned hundreds of rugs, over the past twenty years, always on the clients premises, otherwise, I would have had to charge at least double, to allow for, collecting / delivering, considerably more time handling and most of all aquiring / maintaining suitable premises / equipment.
With the relatively low cost of MOST rugs, very few people would be prepared to pay half the retail value, or more, for cleaning rugs.
If someone has large enough premises and is prepared to invest in the necessary equipment, they could make money, but it will take a sustained marketing effort and you will be competing with the likes of Johnsons the high street cleaners.