If he had no job, was not studying and claiming jsa, income support, esa or similar he would be entitled to a reduced rate of housing benefit (SSR). (£63 per week maximum in 2010)
As he is under 25 he is also ineligible for working tax credits.
The purpose of paying less benefit, is to give an incentive for under 25s to live at home with parents, and to dissuade people (claiming the benefit) from renting privately anything other than a single room in a shared house, it is also there to seek to reduce the amount paid out in benefits. Government agenda, (equality and all that).
However coupled with the demolition of social housing, massive population growth, an increase in buy to let properties and the fact that those under 25 make up the greatest proportion of the lowest paid (and the fact that they are unable to claim WTCs). We end up with the insane situation where people can be better off on benefits, than people working, where there are more homeless people. And buy to let speculators essentially have their houses paid for by state benefits.
After completion of study he will be saddled with debt in an overcrowded jobs market, facing the prospects of taking low paid work or claiming benefits.
Numerous studies out there can be found, linking bad housing to bad mental health, joblessness to bad mental health, lack of housing to joblessness and some professionals even suggest it is better for graduates long term career prospects to go on the dole rather than to take low paid work.
For some of us it is of no surprise a MILLION under 25s are out of work. Quite frankly for many in that age range, they would be foolish to work.
Hence the UK is the successful state it is today.