Psychologically, there is no reason why age would be an objection. Only on the physical side there can be issues, like having a hart-condition, etc. But that would be true for many other substances as well.
You could try a small dose to see how your body responds.
I would say that if you can run for five minutes without getting a heart attack, your fitness shouldn't be an issue. I don't know how it's for diabetic's or people with liver conditions, but you didn't mention any of those things.
Most of the well-known hallucinogens have only very mild physical effects, like a slightly elevated bloodpressure or vasoconstriction. The only aspect where mescaline is a bit harder to deal with than other psychedelic, is it's duration, wich is way longer than most of the other substances.