I posted this answer and then went back and scanned your pic. Edited my first impressions:
If you are buying it from a diesel mechanic who fixes them up then you are/should be pretty much bullet proof from a new purchase reliability stand-point. The tractor looks nice. It looks like a new generator and it also has power steering, a plus but not necessary. The Oil filter is the canister type which helps to prolong engine life....3 plusses right off the bat.
The grill is similar to my '65 but I don't know when they changed it. I do know that around 1970 they went from the oil bath air filter (under that white grill) to a dry air filter which is mounted in the side of the cowl....great big circle on the side, easily recognized and they used a different grill.
Probably couldn't buy a better utility tractor than those Fords. The torque curve, especially on my diesels I'd estimate at about 1000 rpms peak. Even at low rpms the little suckers have plenty of power. They are easy to drive, easy on/off, comfortable riding, reliable, and on and on. You can forget about fuel costs. Those little suckers can go for days on one tank of fuel.
$5k seems a bit high around here, even for a diesel. However with what looks to be a new mower, looks like new paint, and the PS and gen, probably a decent price. 6 speed (3 hi-3 lo) or more tranny and Live PTO are really desirable and could really support that price.
Cracked tires are no biggie but work against the $5K price; look bad but that's about as far as it goes. In light duty, like would occur with a one owner on small acreage, the tires will last the life of the tractor. Your rubber looks ok from here even when blowing up your pic to full screen.
I put new rear tires on mine due to cracking (was redoing paint and all and they distracted from the new paint) back in '05 and the tire size which was stamped in the bottom of the lugs is still visible today. With the price of rubber these days I wouldn't worry about it anyway. My fronts are still OEM best I can tell and are cracked all over but I have no problems with them.
HTH,
Mark