Of course I agree with everyone else on the renting aspect.
I never believed that I could be happy in a job, and I thought that people often placed too much value on happiness in career. My "why" wasn't strong enough. The truth is, my degree and career prospects are STILL not the "why." REI is, even though I haven't *really* started yet. But, since falling in love with it roughly two years ago, my grades, health, and overall life have improved. Religion could be why. Family responsibilities could be why. Whatever it is, you have to find it. That will take a lot of introspect and time.
I'm not a mental health professional. But I have had my fair share of problems. Talking to people, getting out and doing things (like potentially working for you), exercising, and the like will really help. Self-care is not necessarily taking a long hot bath, it's doing what you actually need to be doing to feel better.
I wish your friend the best of luck. Do your best to care for him without hurting yourself.