Please help my little doggo :(

My poor little man potentially has a neurological condition or a tumour from what the vet said. The rough estimate alone for the GA (not sure what that is) and an X-ray is $460.50. And I know there will be further cost.

He can't walk on all 4 legs, his back legs are so weak that he drags them and he yelps in pain when he tries to get up. He doesn't eat much anymore and goes toilet wherever he's lying it's super scary and I'm worried if nothing happens soon it will just get worse

I'd really appreciate it if someone could donate even as little as $1 it will help out a long way, thanks :)