Its not just about pain, its about life long issues with the bathroom, like forever. Plus if its what he is used too, how does he know he is in pain? and not being wormed, do you have any other animals around where you live? Make sure you keep this dog away from where all other animals walk or you risk infecting them with disease he has not been vaccinated from. Unless you plan on raising your dog outside, I would get him in or find someone else who can afford to care for him. Emergency things come up all the time. Please see the thread so you understand what you have undertaken and how serious it is. If a dog need medical attention, you can't put it off.
Cost of owning a dog.