Maybe not the best paid but possible jobs for a teenager to get into are things like painting and decorating, kitchen fitting, double glazing fitting etc. Potentially good money if you work hard. Welders used to be in demand but that was last year. After the collapse in the oil price, fabricators are laying people off rather than taking welders on. Bus drivers are similar to lorry drivers, an ageing workforce but firms still prefer to employ someone middle-aged rather than a youngster for insurance reasons.
Overall he should aim for a building-related trade rather than kitchen work, factory work, unskilled manual work etc. You never know he could be good at what he chooses and later start up his own business.