It is an SR5, or at least it has the stripes, and it looks to be clean. That last pic of the rear quarter panel shows rust, and if it has rust there, its probably on the other side as well.
I bought my 89 SR5 with all power options and v6 for about that much in 2001, but it had a dent on the rear quarter panel and rust spots like yours on the other. My plan was to cut the rust out and put Bushwacker flares over it, but I later opted to have the body work done.
My 89 had 135k on it in 2001.
If you want this truck, take $2600 to the guy's house. Walk around the truck and show him what you are concerned about. Don't insult him, but be honest. Point out the rust. Take off the panel from the inside and you can see the rust spreading. Offer him $2300, and see the response. He'll probably say no, so then look it over a bit more.
Before you leave, say " OK, you want $2800, and I want to pay $2300, can we meet somewhere in between, like $2500?"
He'll either say yeah, or say "$2600" and then you just counter with $2550, or say "yes, $2600, but with a full tank of gas" or "yes, $2600, but you buy the beer" etc...
It's a nice truck with very low miles for the year.