So basically you've found it hard to be firm (i'm a bit soft too) and created a dependant man child.
Do you really want rid or do you want him to grow up and contribute?
Write a list of all the things you do, all the things you pay for i.e. electricity, wifi, tv licence, sky, fuel, council tax, roof, food!
Work out what rent for a room is locally,
Tell DS that he needs to set up a standing order to you weekly/ monthly on payday for this amount from next pay day or the locks change.
Be prepared to bolt the front door and use the back one etc on that day. Fit a large bolt a few days in advance to make it clear you mean business. He may need a few days sofa surfing to realise he needs to take some responsibility and contribute. You need a cast iron will if you want to reverse the situation you're in.
If he starts to pay and you allow him back then work out how much deposit is etc. to set up on his own. If its £1000 and rent is £100/week then your DS needs to pay this amount for 10 weeks (or equivalent monthly amount). As the point approaches that he's paid enough to you to cover deposit and first months rent on a place decide if you want to pay that on a place for him and send him on his way or start introducing contributions for food, bills and chores to stay at home.
All looks so easy written down but the reality is no doubt tough and you need to be clear and calm in your instruction to him. Maybe even write it down for him.
Is he in debt or is he just living a month in arrears enabled by family/ friends/ overdraft?