I was 33 when I applied and approved for SSI disability. I was approved the first time, and my interview was over the phone, it's my understanding (therefore not necessarily fact) that a stage IV cancer diagnosis is generally approved without out much hassle.

http://www.ssa.gov/disability/

There's the link, I don't remember much about the process as my wife handled it, I do remember the interview though. Memory is very "hazy" due to all of the drugs, but I remember that we didn't have to jump through too many hoops. My wife is really good at paperwork too so that probably helped.

Good luck, hope it helps

Eric