Depends on who owned it before and how well they maintained it. With proper maintenence the 7.3 will probably live longer than you will. The main things to look for at that mileage is hubs/bearings, transmission, u joints, and steering issues.
I just bought a 2000 F-250 Crew cab, Lariat, 2wd with the 7.3 and Automatic tranny. 234,000 miles. I have a manilla envelope with receipts all the way back to 20k miles.
The oil pan is a big thing on these trucks. The oil pan cant be replaced without pulling the engine. There is a crossmember that sits about an inch from the bottom of the pan. Look underneath the engine for rust and major leaks. Minor leaks are going to be normal at that mileage.
ALSO - when you go to test drive one of these trucks, MAKE SURE it is DEAD cold when you get there. Pop the hood and reach to the back of the motor and feel the turbo. It should be dead nuts cold. If it isnt cold, the owner probably warmed it up before you got there (might have cold starting issues). As previously mentioned, extended cranking isnt necessarily abnormal, but on cold start idle, it should not chug, shake, or smoke (white or blue).