How much can you earn B4 paying tax

[Cobwebs]

My friend and her husband are unemployed but she wishes to get a part time job to fit in with the kids school hours. Neither her or her husband claim benefits for themselves (no dole etc) but she gets child allowance and family tax credit to the tune of around �130-150 per week. (her husband can claim the dole but he won't - reckons its demeaning!!) Anyway she has 3 children at school. How much can she earn before it effects her benefits or b4 she has to pay tax. She has been told a various things by various offices varying from �20 per week to �4K per month. Appreciate any advice you can give!!