Wakeupcall, I did that too, at one point with my son. Slowly, I quit paying for every single thing until I wasn't paying for anything.
I think the phone is often the last one to go because we think we need to have a way to contact them. I finally learned that they will find a way if they want to contact us---my son started using facebook messaging, he found some kind of way to text message me from his old computer to my phone (???), and he would borrow other phones.
At one point when he was homeless four hours from here in a major city, and living at a McDonald's for 30 days, he made friends with the staff and was sitting up in their back room, eating food, smoking their cigarettes and using their phones. All that time, I was in agony thinking of him huddled outside against the air conditioning units over the coldest days of Christmas and New Year's.
It is truly amazing how they can and will survive. We can't imagine it, but most of our off-the-rails kids can endure what we would believe impossible conditions, and only in that way do they finally hit a bottom---years after we think we would have hit it 100 times already.
I think we can feel clear about the facts that our sons are grown men. They are adults (albeit children in adult bodies, perhaps). It's way past time for them to take stock, make something happen for themselves, get the help they need to function in society, and start taking responsibility for themselves. If not now, then when? If we keep on, they will never have a chance to find out what they are truly made of.
If his dad wants to take this on, he will. And you'll have to let that go, too. But slowly, he will stop, or he will not.
Rest in your decision today, and live your own life. Believe me, he will surface again. They always do.