If he's employed (full-time or part time), then he'll have a P60 at the end of each tax year..... unless it's undeclared income.
The P60 represents what he's paid in tax, and what his employer are paying in National Insurance contributions.
If he's working on a "cash in hand" basis, just be very, very careful, and be aware of the potential consequences.
Also, £440 income per month is very low. I'm assuming that he lives at the family home, so has no/little outgoings ?
If so, make sure u read the threads about (suitable) accomodation and confirmation of support/change of tenancy by either the householder or landlord.
