I was in a very similar situation with my Beagle of only 10 years old. She developed breast cancer. No visible signs of anything except a bit more fatigue.Spent the initial $475 and then she was scheduled to have the $650 surgery. 2 weeks before surgery, she got REALLY bad. Tired. Vomiting blood. No solid waste. Paid the $165 for euthanasia the following Friday (3 days) after she vomited blood.
Like a blind man at an orgy, I was going to have to feel my way through.