Help my pet rat Joe get neutered.

Hi, my rat Joe is around 6 months old. Recently, he’s been getting in fights with his brother Gubbs. This is because Joe is hormonally aggressive. I love Joe so much and neutering him is very expensive and not within my parents' budget at the moment. The only other option is to rehome him, which is the last thing I want to do.

This is not an emergency, but I don't want him to be separated from his brothers for too long. Anything will help, I am not expecting to reach this goal but even hitting like 50 dollars is good.