You don't say what it is, make, model, gas or diesel? Most likely a GM product. When I drove for a living our operation sometimes rented straight trucks but never from U-Haul. Ryder was much preferred and we knew they maintained their vehicles well. 230K is high for a gas engine but middling for a diesel if well maintained.
Does it have a liftgate or a loading ramp? Liftgates are costly to have repaired. A lot of rental box trucks have sustained accidents and/or cargo box damage and the rental places don't often do a good repair job. Odds are the one you are looking at is under 26,000 GVW meaning anybody with a regular license could rent it. Meaning most of the drivers are clueless as to driving a large vehicle.
Depreciation on a medium duty truck is frightful. My last work truck was a bare-bones F-800 diesel with an automatic, 20' box, and liftgate. Buying thru the fleet service at max discount it cost my employers about $65,000 and six years later, at 50,000 miles it was auctioned off at $10,300 and it still looked and ran like new.
I would steer clear of the one you mention....too much money AND TOO MANY MILES.