Thanks for the help!
After I checked it out, there was a significant amount of rust on the undercarriage. Way more than my Tacoma of the same year. I didn't see any growing holes or obviously ruptured welds. There was also some major rust on the seat hinges (weird) which I guess could have been from spilled drinks. But it was on both sides of the middle and 3rd row seats. Could have just been from being a 14 year-old vehicle.
With the amount of rust, and since this truck started its life in Maryland, then moved to Arizona before coming to WA, I decided to pass.
I'll keep my eye out for another Sequoia, though.
Welcome to the forum. You already got the timing belt/water pump out of the way so just look for under carriage rust. You will find these forums helpful too. Toyota nation forum and Tundra solutions forum.