From a buinsess aspect you also have to look at the return period.
Take £500 work in a day. This would cost me £180 wages, £75 VAT, £60 tax/Ni leaving a net profit of £185
Based on a monthly visit and a sale value of 2.5 times monthly gross this would take me almost 7 months to recoupe my outlay. If you charged based on annual turnover i.e £500 x 12 = £6,000 (say ask for 50%) this would take me 16 months to get a return and that just isn't viable?
I also appreciate your thoughts Sunshine but also consider that I guess most of the work is domestic and if commercial on contract, but like everything, nothing is really guaranteed so if you take 7 months to recoupe your outlay it also gives you 7 months to have customers cancel through moving, unhappy, etc.....
Well there ya go for what its worth
best wishes, Trev