he has essentially already left the marriage by moving into the basement and getting his own checking acct. the light was just his excuse as already stated. this is his issue, not yours. he's made the choice to be a room mate and wanting one with benefits. you do not have to tolerate that and he shouldnt be living there for free. he should be paying his half of the bills and making his own meals. no benefits. marriage counseling could get to the root of what happened, but whatever it was, it has been brewing for a long time.