Given that it's questionable whether I'm going to have enough finite resources to bring my aging cat to the vet in the near future; and I live in Canada, with its single-payer health care system; it's a somewhat more complicated question than it may seem. Given past evidence, some minimal qualifications might involve me knowing that you exist, and knowing that I was able to help you, and knowing that the help I could provide would make a difference (this latter being one of the harder qualifications to satisfy). Given all of /that/... one potential qualification might be the possibility for future reciprocation, either directly, or by being part of a shared, low-population social group in which your future contribution could still end up benefiting me - such as, say, the two of us being part of a literally-one-in-a-million group working together to try to find some way to permanently cheat death.

There are probably other answers, including ones that I don't recognize due to my limited knowledge of human psychology and my finite insight into my own motivations... but that one seems to have some measure of plausibility.