It's sad that you doing a good turn to someone has turned out like this.
Did you, at the outset, lay down clear house rules - eg his monetary contribution did not include certain things, expectations as to keeping his room/the house tidy, care of clothing, etc, etc. Young people are often unaware that leaving lights on, using lots of hot water, etc, etc, incurs substantial cost. Of course, you would expect a guest in your home - especially one that you are doing a massive favour for - would be on their best behaviour, but I don't know what this person's background is. Perhaps his life has been chaotic and he has no idea how to behave.
Having said that, I think you are perfectly reasonable to ask him to leave, especially as it appears he hasn't understood that it is he who is at fault - since he has been complaining to a "mutual friend". I would suggest that mutual friend takes him on - and good luck to whoever does.
Sorry, I have just seen that he has gone - but I think my comments are still relevant.
I can understand the OP being reluctant to help anyone out in the future - she has been very patient.