Buying something that is still supported by the manufacturer seems a sensible precaution when buying high priced second hand audio items, IMHO.
Otherwise, I'd suggest to go for "bargains" only and accept that there is a high degree of risk - especially as audio users damage things quite often (a blown tweeter, a fried amp or a bent stylus being par for the course for anyone serious at this hobby...in fact most loud house parties will usually blow a domestic speaker, as they just aren't up to that kind of abuse)
Otherwise, I'd suggest to go for "bargains" only and accept that there is a high degree of risk - especially as audio users damage things quite often (a blown tweeter, a fried amp or a bent stylus being par for the course for anyone serious at this hobby...in fact most loud house parties will usually blow a domestic speaker, as they just aren't up to that kind of abuse)