Simba's leg amputation and recovery

This is Simba,  he's just one of my rescue babies.   He developed a tumor on his paw a few years ago and I had to have it surgically removed.  The tumor has returned and grew extremely fast.  When the doctor saw him she said his leg had to amputated as soon as possible because it's a cancerous tumor and will eventually lead to death.  I have tried finding an animal doctor that can help me  but no one will help me with billing  ( a payment plan) and I don't have the kind of money they are wanting.   During the covid 19 pandemic I've been out of work and barely keeping my head above water.  I just started a new job but I'm playing  catch up.  I don't want to put Simba to sleep because of this.  He's been in my life for many years and he's happy but obviously showing signs of pain.  Please help if you can it will be very much appreciated by Simba and myself.