Peanuts? You were lucky to have peanuts! We had to work 22 hours a day
for a bag of cold gravel...

You don't pay them less than the minimum wage. It's not a difficult
concept really.

I don't really understand your question - the minimum wage is just what it
says.  The employee cannot even out out of it if they wanted to.

The only possible way round it I can think of is if you offer accomodation.
That MIGHT be classed as a taxable benefit and therefore part of the salary.

Let's be honest though - the minimum wage is peanuts anyway.

You get paid the minimum wage.  

There is probably a tendency to employ fewer assistants than before.
You might find some photographers will allow you to accompany them in
order to watch and learn (but not work) for no pay.

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Don't rely only on the min wage as a guide. Experienced assistants should be
getting ca £100-120 per day, more or less... and that is just the starting
point (in cash) depending on what else you are willing, or not, to throw
into the deal (travel costs; meals; ect)

If you are willing to tolerate someone with no, or little, experience and
trade that off against constant supervision of the assistant and that level
of required supervision against lower production output... well you get what
you pay for, probably not unlike the old movie character of *Stepin Fetchet.

*Stepin Fetchet: The prototypical, pre-PC, movie "coon" was Stepin Fetchit,
the slow-talking, slow-walking, self-demeaning nitwit. It took his character
almost a minute to say: "I'se be catchin' ma feets nah, Boss."

Journalist