Save my best friend Saben T.T

Hello everyone my cat Saben is only 6 and he is very very sick. He won't eat or drink. he can barely walk, and he is retaining fluid in his abdomen. The vet said that it could be cancer but we can't afford a biopsy or treatment for whatever they discover. He has been my best friend my whole adult life and he always could tell if you were having a rough day. Through everything in our lives he's has always been there purring and locking the tears off of our faces. It wouldn't feel right to just put him to sleep without finding out if there is anything I can do for him first. My fiancé and I just adopted my three little sisters and both work full time just to pay the bills and feed everyone. Please pray for us and if you can spare anything you are a blessing.

Ps any money leftover after the vet bills will be donated to the humane society and I will post proof