He pays no rent, contributes in no way to the household, brings freeloading friends around the house

Change the locks! Then take all of his belongings outside with an invitation to leave.

If he refuses to go, put in a call to the Police and tell them you have trespasser on your property.

Been there, done that!

This is a legal question so has been moved here. The reality is that your son is a resident in your home. As such he needs to be formally evicted as any tenant would. Laws do vary, but if you forcibly remove him (i.e. change the locks) without a court order, then you open yourself up for a lawsuit for illegal eviction. So its best to be on the safe side and follow the rules for an eviction in your area.

You can find these rules at your local housing court. Generally you give him a 30 day notice that you are terminating his tenancy. If he still refuses to move you file for an eviction order. A hearing will be scheduled and afterward an order will be issued. If he refuses to comply with the order, then you get a sheriff to physically remove him