In need of life changing surgery!

I'm 32 yrs old, and have tried many different weight-loss systems. I am now begging for help. Surgery cost about 40k for gastric bypass for my size and condition. I am disabled because of my size and unable to walk more than a few feet with out having to sit down to get the weight off my knees. I hear alot of people saying to just walk and I wish I had the ability to do that but now my knees are too bad to hold my body up long enough to walk. I have tried getting state assistance in the past with failure so now I am asking the public for help. I have 2 step kids 8, and 5 I would like to see them grow old and with out this surgery I will never be able to do it.