If I was employed full time as a canvasser by anyone, I would want to know what was expected of me to succeed and I would want to know what the long term prospects were/are for me. I would also want to understand how my employer would handle those leads or customers I signed up as it would be important to my job satisfaction.
A short term canvasser will be told that X number of leads are required and this is the pay. If any of those drop out then they are either replaced or deducted from the bill.
Ian's experience is probably much better than mine, but how many leads can you process a day? In other words, if I got 5 qualified leads today, and 10 tomorrow and 10 the following day, are you geared up to do all those first cleans and integrate them into your customer base? As you are slowly growing your business getting another franchisee on board and up to speed doesn't happen over night. Have you got time to do both?
I would also consider that 10 leads at £15 average per clean isn't going to pay my wages, even if a first clean premium is obtained.
I would immediately realise that my future career prospects as a canvasser with the business hinges on how well you, as my employer, handle those leads. If you can't handle them because you haven't the infrastructure or staff to do it, then my job won't last long.