Don't read into mileage too much. I made that mistake. Bought my focus at a screamin price, it only had like 53k miles on it (and it was ~5 years old when I bought it) and was by far the lowest mileage focus in my price range. 10k miles later, I replaced the engine because the previous owner apparently either a) drag raced it and blew some seals in the engine, leading to massive oil burn and low compression or b) didnt bother to change the oil and totally effed the thing up. Just make sure the car was well taken care of and listen for any weird noises.
ROTM June '13, PNW Crew #42, SR #245, Rally Rev #02