Dan,
In some ways I have to agree with Melanie, though her delivery leaves something to be desired.
It sounds as though you haven't made any purchases as yet and you have had a chat with the landlord, he has offered you the job (if the price is right) and you are now looking into it further, which is the correct way to go about it.
However, I have just looked on yell.com and there are already A LOT of carpet cleaners in the Exeter area, including several who are paying out £,000s for an enhanced listing and web link on yell.com. It would be interesting if Melanie filled out her profile so we could see who she is and who she trades as!
Getting just one pub job doesn't justify investing in machinery and advertising, or even guarantee that you will get another job! Competition is fierce.
Pubs are often the worst jobs you can do, their carpets are generally baked and inground with chewing gum. There is a good chance of shrinkage depending upon the carpet type, especially if you don't know what you are doing.
Even now I still hate doing pub carpets and we have probably 50+ pubs on our books as regular customers
They are also often looking for the cheapest price and also an almost impossible "as new" finish. Don't expect that just because you did it this time that it is a guarantee repeat business, there is a good chance that the next "newbie" to come along will get a go for even less money.
Ask yourself, why are they asking you to do their carpet if you haven't ever done it before?
Don't take this personnally but they are obviously not looking for the best quality of service as you have no experience, they are not working off recommendations as you have nobody to recommend you, they are basically looking for someone to do it cheaper than it was done the last time, but they will expect the exact same quality of finish, or better! Are you able to give them that?
The title of your thread relates to price, so you are also obviously primarily interested in how much you will get for the job. Personally I would go on the course, see what's involved, test the market for prices and opportunities and then, if the work is there, look at purchasing a machine and making a go of it.
I would say though that the Exeter area looks pretty much saturated now will carpet cleaners of all abilities and prices