It's absolutely OK for you to say no. I wouldn't fund any of those things. Nothing you mentioned is a necessity. Physical exercise best treats depression and anxiety. It's time to sit down and have a real-world discussion with him before this gets any worse. If he wants a cell phone and car he needs to work. Unless you are prepared to pay for his addictions his whole life, it's time to end this enabling behavior. If he wants real treatment for anxiety and depression, then pay for that.