I disagree with your post. You will get SSDI when you have over 10 years of productive employment. I had SSDI for four years, starting with California. The amount was high, but eventually I moved back to Las Vegas after I graduated from SFSU, my SSDI amount was decreased a little bit (I don't remember how much). Then, I moved to PA for a job and asked SS Office to put me on Work on Trial for 9-12 months. The amount was the same as far as I remember.
But, I guess the rules of SSDI and SSI vary in different state.