I am right now applying for SSDI/SSI. SSDI is basically for people who have paid into social security that become disabled before they are old enough to collect on their Social Security. SSI is basically a government form of welfare and is usually for people who have not paid into Social Security or who have not worked long enough to qualify for SSDI. I am applying for both because one of my parents is on SSDI and I am under the age of 22 and you receive more money that way. I did get denied on my first try and I then got a lawyer (Binder & Binder). I found out that they can ONLY take 25% of your back paid owed or if you are owed a VERY large sum and the 25% is more then $6500 they can only take up to $6500. I believe Social Security has imposed laws (Social Security has to approve your lawyer first, they do that to protect you) saying that if your lawyer does not win your case they can't charge you anything. I have heard pros and cons to getting a lawyer, but I personally believe that they do help and Social Security takes a shorter amount of time with the lawyers (plus they know the ins and outs and I don't lol). I hope sharing my little bit of info has helped and PM me anytime if you want more info.