Legally, as an adult you are no more obliged to allow him to stay in your house than anyone else and are entitled to ask him to leave on virtually no notice, though you do have to allow him to collect his things.
You can call the police if he won't leave or change the locks (if you own the property - you would need the landlord's permission if you are a tenant).
Likely you need to explain this to him and if he threatens you or you find his behaviour menacing such that you can't deal with him you should again go to the police. If they won't help you you can go to a lawyer who can arrange for a restraining order against your son. You can read about such orders here, which can include an order by the court that he leave the home and not approach under threat of immediate arrest.
All of these are of course drastic measures but they are legal options.
You could also start with a less drastic option of family mediation which might perhaps be a good way of approaching him about the reality of your situation and the need for him to either contribute and improve his behaviour or move out and such could be arranged through an organisation such as Relationships Australia. You will have to judge what is the best approach as you will have the best insight into what is driving his behavior.
I trust the above assists.
Good luck and PLEASE RATE MY ANSWER.