I bought an '87 Samy from a private party with 40,000 on the odometer. But he told me the mileage was 140,000, he bought it new for his daughter who used it for college 5 yrs and for work 2 yrs, he then took it back and used it as a tow vehicle.
Assuming 12,000 to 15,000 driven miles per year, and 30-40 % towed mileage per year the 140,000 is about right. Look at the other tips listed above, and trust your guts as to the integrity of the seller. Mine was a positve experience. Good Luck.
BTW - they make an excellent tow vehicle - less than 1500 lbs don't need brake buddy. Goes anywhere road clearance and overhead clearance allows without going too extreme. I use mine to explore off road areas in BAJA.