storm4star has got it right. Kicking someone out with no structure or job is unlikely to result in them suddenly finding a safe apartment to live in, getting a job, standing on their own two feet etc. Like storm says if he's kicked out without a plan, he most likely would sofa surf and sadly, from the sounds of it, turn to crime as well. There needs to be some kind of plan or structure in place.
If you can talk to him, I'd sit down with him and ask him what he wants for his life. Explain that this situation just can't go on, and it's unlikely to make him happy either. Does he want to be living at home in 10 years time? Or does he want some independence? What kind of job could he do? Or would he rather an apprenticeship or college course? This is the key to it.
What is his current college course and what does it lead to? Qualifications? Some courses don't have many contact hours and are actually good courses that lead to recognised qualifications that help with getting jobs. Would you be happy if he carried on with his current course and got a part time job. (It's hard to advise without knowing what the current course is.)
However, things around the home would have to change. If he wants to stay there, I think he should keep decent hours, if he can't have a key to let himself in and out, then there needs to be reasonable set times. Which tbh I would've massively struggled with at 18 (but then again I wouldn't have misbehaved to the point I couldn't have a key I think).
I don't think his room is an issue at all, it's his room, he could keep it how he likes as far as I was concerned, as long as it wasn't unsanitary. So pick your battles.
"He has no income so we're paying for everything" - that needs to stop (unless he is in full time education, when it is a bit more reasonable).
This is a make or break time in his life. He's 17/18. His life can go in different ways depending on how its handled. Tread carefully, and if I was you, I'd get outside advice, not from here. Storm is right that his life could spiral and end terribly, but equally, the current situation cannot carry on. Surely there is some way to work out, with him, a solution to this.