Why not take a look at what your man uses ? I feel you're thinking like a House Cleaner who takes a team of cleaners around which is quite different from Carpet Cleaning
he uses an ashbys ninja. seems like a good machine but wanted the opinions of others. you're correct we are a house cleaning company (mainly doing one off cleans) and would be taking around a team of cleaners, so it makes sense to keep the carpet cleaning jobs one day as it can often pay more and be there a tiny fraction of the time that we are there for, e.g. today 4 of us cleaning 6 hours get £255, carpet cleaner there an hour gets £100, one day i want that to be me 
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Lets think about this logically. I am not knocking your idea, but you do have a lot to think about. Your example job 4 cleaners 6 hours etc.If one of those 4 cleaners is the carpet cleaner for one hour, your hours are straight up to 7 for the general clean. Someone already said the 2 don't mix well and they don't, so your general cleaners have to be out of the way whilst the carpets are being cleaned. What will they do, just sit in the vehicle being paid to do nothing? Not good. Whilst you may think every potential customer will want carpets cleaned, this is not reality, and some prefer to use independent carpet cleaners anyway. £100.00 per hour?
? in your dreams sorry but you you may get an hourly rate like this once in a blue moon, but not on a regular basis. You cannot expect to pay an employed carpet cleaner at £6.50 per hour as you would a general cleaner. It's hard graft and speciliased work. You would be better off building a stand alone cc business and still utilising your subbie for the time being, whilst you get training and experience. 
we have worked with the carpet cleaner for 6 months now and it's never been a problem that we work along side him, it's very easy when we work like this, we start rooms with carpets, then do rooms without carpets while the carpets get cleaned. it really works well and would work in the future. i suggest anyone try it if they think it doesn't work.
we already have 2 small cars which we use and would continue to use if it was ever the case that the carpets would take longer then the clean. the cars we use are too small for what we do now anyways, so we need a bigger vehicle. makes sense to get a vehicle now that'll work for carpet cleaning when we start the work in the future which could be 6 months, could be 1 month, could be 2 years.
we also are the ones who price for carpets, so i know what he gets paid for the carpet cleaning. £100 of course is one off sorry if i sounded like i thought it was all the time, but it's very close to it more often then not. we did another the day before and we got £170 whilst he got £230 and was there around 2 hours at the very most and that included a long chat with each of my workers.
to the person who said about not being as good as the guy we use, are you saying i should never start carpet cleaning and nor should anyone else as they wouldn't immediately be as good as a professional that has been doing it for a couple of years? seems like a silly thing to suggest imo. i clearly haven't just randomly jumped to saying i'll do carpet cleaning tomorrow and be an expert, but instead said that i want to be prepared now before start cleaning. in my first post i even mention training courses and ask for advice. if you think i need months of training courses say that instead please.
thing is carpet cleaning can be "hard" work as in requires a lot of knowledge about what is best for the problem, but it can also be incredibly easy work, i know as i have a good relationship with him.