Well, you can direct him to AA or NA. They are free. He needs to go daily and get a sponsor. If he needs rehab, there are low cost/free rehabs, it's just that there may be a waiting list.
Here's what YOU can do. Exhale. Calm down. Panicking won't help but setting boundaries will. It's ultimatum time: He either gets help now (not tomorrow, now) or he can't live with you. A 27 year old living at home w/ no job is a recipe for disaster for an addict. He is getting the money for drugs somewhere. Oxy on the street is insanely expensive. Do not give him one dime of actual cash. You need to be stronger than you've ever been and not cave no matter what excuse he comes up with. That's the using addict's mantra: "I can't, I want help but I'll get it tomorrow." No, today or leave.
I would strongly recommend you get into Alanon asap as well for you. You will meet tons of other parents, siblings, spouses who have been tormented by a loved one's addiction and are learning to be serene no matter what the circumstances.