sending a letter saying you are disabled will hardly matter. You need to be diagnosed disabled by a doctor. You really, really need to be unable to work, and have unable to work for at least a year, possibly for the rest of your life. You need mountains of documentation.
I will also ask, what is the attorney's track record on SSDI appeals cases? Is that what he normally and exclusively does? If he's simply willing to take this on but normally does other things, that's a huge red flag. If I've misunderstood, and yes, this is what his entire practice is about, I apologize for being so skeptical. It's just that what I learned during that internship was quite eye-opening, especially the part about people don't understand what is really meant by being disabled in the eyes of the SSA, and how much documentation is needed.
My brother was fortunate, in a bizarre way, that by going blind he qualified immediately. He's 70 now, totally and completely blind, and is incredibly cheerful, for the most part, about his situation. My sister and I really wish we could persuade him to move to some kind of assisted living, but he's not willing. The essential problem there is that he can still find his way around the small town house he lives in. He knows where everything is. A new living space could be very difficult. Plus, negotiating the public spaces would be almost impossible, especially as he never learned to use a cane, and getting a guide dog is probably out of the question at this point in his life. Fortunately, he has some good friends who look out for him, and decent services where he lives, in Tucson, AZ.