OP does your son pay for his own internet supply? If not, then I would suggest changing the password, and telling him that he needs to get his own. I would also insist that as it's just the 2 of you living in the house, that he pays half of all household bills. If you rent, he must pay half the rent, half the gas, electric, water, council tax, etc. If he says he can't afford it, then tell him that he is now of an age where you no longer have a responsibility to pay for the roof over his head, and therefore he must get a job that pays enough for him to pay half of the living costs. If he refuses, then tell him that you are giving him 2 months (or whatever your feel is reasonable) notice, to find himself other accommodation, and MEAN it!! Tell him that if he can't pay his own way then you'll be getting a lodger in who will. Maybe even go so far as to ask your daughter if she has some mates who would be willing to pretend to be looking at the property as 'prospective lodgers'. Do it while he's there, and introduce them as such. Maybe that will be enough to get him to pull his finger out.