Warning you in advance, this is a long response
Be prepared for a long and drawn out process, in the end it will be worth it but while you're going through it you will feel like your loosing your mind.
My Husband qualified for SSI disability last June. It was a royal pain in the butt with all the paperwork and questions. It took 5 months after the first interview with social security to get an answer. He was one of the very lucky ones who got it on the first try. About 70% of applicants get denied the first time. He has Parkinson's disease and had worked as an auto mechanic for 30 + yrs.
When you call to make the appointment they will send you a huge stack of papers to "prepare" for the initial interview. I made sure we had all our bases covered, from making sure all of his doctors knew he was going to file to keeping 100% accurate records of when and why he was seen by each MD. He had seen many specialist, Psychiatrists, Psychologists, Neurologists, Orthopedics, and of course his Primary Care. All of these Docs will be sent letters requesting your medical information and input on how you rank on the disability scale. When you go in for your interview make sure you have all your doctors names, addresses and phone numbers. Also include what medications you are on, who prescribed them and what they are for. I typed out a list, it went much quicker, the interviewer just had to enter the information into the computer.
They ask a lot of questions that you wouldn't even think of unless you have gone through the process. Such as what percentage of your day at work is spent walking/sitting/lifting etc.. How does your disease prevent you from performing your job and why (they want specifics) How much pain are you in on a scale of 1-10 ect... How far can you walk? How long can you sit? How many lbs can you lift & carry( I think you get the picture)
After the interview most of the time they will send you even more paperwork to sign, make sure you don't miss a thing and mail it directly back to them ASAP. Most of the claims are rejected because someone has forgotten to sign something. ITS MIND BLOWING to say the least.
The final step is usually an examination by an MD chosen by social security. His evaluation is probably the most important one in this process. Most of the time the MD is retired from private practice and just does SS evaluations so he absolutely is very particular about his recommendations.
We managed to go through the process without a hitch, but you have to read the fine print and above all stay organized.
I hope this has answered some of your questions, If I can be of anymore help just let me know
Take Care and good luck