Should I have taken him to the vet?

a stray cat that i'd been feeding and given a makeshift house of blankets outside my house today died! it had a bad cough and was very weak for the few months I had it, also had a bad wound under its arm that I think might have got infected. I'm feeling guilty now because I think he might've been alright if I'd taken him to the vet, I never thought he would die so quick! I just thought it would cost a lot of money and I don't have that much, also i have another cat that I actually own and need to pay for, was I wrong not to take him to the vet? I was also afraid they might have put him to sleep, because he seemed very ill, and I didn't want that to happen, which is another reason why I didn't take him :(