What's the best choice regarding this rabbit of mine?

Please ignore the stupid advice of breeding them. That will only make the problem much much worse. Surely you can afford just to get him neutered for now? It is not expensive and it is essential. Your females also need to be spayed to reduce the risk of them getting ovarian cancer. I am very disappointed that you have four rabbits and yet did not consider the need to have money for trips to the vets. Can you honestly say you could give up your little rabbit just because he spays? It just seems so mean. I can understand how annoying it is for you but this is not his fault and he cannot help it at all. Maybe you could sort out a payment plan with the vet or borrow the money to have it done? If you really cannot wait until January then it is not that far away but will you be able to get all four neutered or spayed? If you take him to an animal shelter and nobody adopts him he will be put down and breeders do not buy animals. They just breed them to make money.