How much Social Security (SSI) could my son receive?

I have a two year old with severe autism I just applied for SSI for him about 3 months ago and I was curious as to how much he could receive? Right now I am just a student living with my grandparents. I have no income besides my STIPEND checks. I am a single mother and am trying to receive cash benefits through welfare., I have no time for a job my 2 year old has a lot of therapy and my 7 month old is developing slowly also. But anyways what is the most SSI will grant my son so it can help with diapers, clothes etc?