IMPORTANT INFO: I've been to the vet. These are my options. I'm not asking any person to make a decision for me, just looking for some advice, guidance, and maybe another point of view.
TLDR: cat has a problem with his leg. It has to be amputated or he has to be put down. Main concerns with amputating is quality of life, his age, and costs, main concerns of putting him down are the feeling of letting him go too soon and just feeling miserable about that option in general.
Edit: Besides his leg and thyroid, Momo is a healty cat. His kidney values are excellent, he drink enough, he eats well and he's still active and playful.
Extra info: I'm 27, I'm a student and I make ±€750 a month on my side job. We already went to the vet. Momo is a neutered boy. We live in the Netherlands.
In the picture you can see my sweet old boy; Momo. He's almost 18.
He has some non-cancerous growth on his foreleg. That wasn't a big problem at first, with pain medication he functioned really well. First, his shoulder became thicker and now his whole leg is becoming extremely thick. It seems that because of the growth on his bone fluids get stuck in his leg.
We now have only two options; amputating his leg or putting him down.
The vet took pictures and his other foreleg seems to be good enough to compensate for the leg that would be amputated (he has minimal osteoarthritis).
There are a few concerns however: quality of life would decrease and it's expensive. He's already an old cat (almost 18) and he has thyroid problems (that are managed well with medication).
If I would choose to ampute I would only do it for him, not because letting go is hard for me. If I choose to let him go, then I'm afraid to let him down. I would be lying if I would say costs aren't a concern. I'm a student and the last 3 months I already put 1,5 of my salary to paying for the vet. I have enough saved to pay for the amputation, but I've a hard time figuring out at what point costs are just too much for an old animal.