With full warranty, I assume it is sold from a dealer. If the dealer rented it out a few times, full warranty and that few of hours, I would not be concerned. Take a look at it. If it is in very good to excellent condition, I would not have any problems buying it. I look at it this way, it has a few hours and therefore, you should be getting a good deal on the unit. 300 hours is nothing in the life of the tractor. I actually prefer these kind of deals because you should be able to drive a good price. Have them change the oil, filter, HST fluid ect before you buy it, unless it had been very recently changed.