My first Expedition was a retired SSV. It was a 2002 with about 35k on it when I bought it. I sold it at around 125k. No major issues.
At that time, SSVs had cloth front seats, vinyl 2nd row seats, and no 3rd row seats. It also had a rubber floor mat and no console. Other than that, it was an XLT.
As mentioned above, 4th gen SSVs have a column shifter for the transmission which you've probably already identified since you know it doesn't have a console.
There may be holes in the roof where antennas were mounted. Or, they may have simply removed the antennas and left the antenna mounts. The mounts are probably NMO mounts which are about a half inch tall and have a thread that's about an inch in diameter. If the NMO mounts were properly installed, they are nearly 100% water tight. You can get NMO caps if you want to dress up the bare mounts.
I would ask to see the service records. If the vehicle has been in a fleet, it was probably well maintained according to the factory maintenance schedule.
I think there's a way to see the idle hours on the vehicle. Extended idling qualifies as "severe service" so hopefully that was taken into account in the service intervals.