I would deffinately get a second opinion,talking about aputation just because you cant pay all that money at once is just not fair on you or your baby at all..who has that kind of money these days anyway?? ALL of our vet clinics offer a payment plan,especially if you are a regular patient because if one day a car was to hit some ones baby,or someones dog suddenly gets sick(example),the bills would be very high and no one can just pull money out of thin air,so the payment plan is there to make the owners life a little easier and so that the poor dog has a chance of being saved.There must be a vet out there that does this kind of thing so I would start searching if I were you.The vet you have now doesnt sound very nice/understanding and he also doesnt seem to know how to put a cast on a dog..I would deffinately try and find another.Good luck!! I hope your babys leg is better soon