only pay minimum wage or thereabouts to start off with. there onwards pay bonuses for good work, reliability, new sales, whatever.
if they want more money they have to take more responsibility on board and prove they're worth it.
its very easy to over pay at the start and then regret it later, as you have no way to add bonuses or responsibilities without them complaining or without increasing their already hi wage.
if they re paid cash in hand they're receiving subsidies off the government in effect anyhow so i'd pay £5 an hour of £30 a day or something.