For me, it would need to be in pretty much showroom condition, and absolutely everything should be in full working order.
I would want to go through the service history to ensure that it doesn’t have a troubled past, and has been properly serviced.
If it passes those tests, it should be OK: They are reasonably bulletproof.
I have had my XK for five trouble free years.
I looked at a few at the time but, until I found the one that I bought, none were in the kind of condition that I wanted. As soon as I saw mine I pretty much knew that I was going to buy it!