That looks a bit crusty to me. I get between 11mpg in heavy city traffic and 15mpg on a run most of the time. Very occasionally I've seen better, as high as 19mpg, when forced to drive slowly but 14/15 is more realistic if you enjoy driving 

seen a lot worse mine was crusty but when i felt iside chassis it was smooth ,but they are old i re waxoyl mine every year just for peace of mind
TOTALLY AGREEThose photos show some rust. Not TOO bad.
Does anyone else here think that looks like it’s been undersealed at some point?
The positive thing here is that the owner is happily sending you photos from underneath. Without trying to do him wrong, he could be missing something. It’s not rust free but it doesn’t look beyond Fettling. If the rust is on the surface it can be stopped with Krown but if it’s gone through the only option is to cut it out and either weld in new metal or fill with a grommet if it’s a tiny hole in a sill for example.
Your first pic shows a tiny hole near the sunroof drain pipe (angled), Pic 2 looks most awkward with some flaking which is what makes me think underseal but I’m by no means sure of this. If it has been then it could be hiding all sorts of rust issues. If not then what’s shown in those pics doesn’t look ‘walk away’ terrible.
I have a 100 2004 with only 89,000 miles, I agree 92,000 is hardly 'Run in' for the mechanical side of things just as long as the mech items have had the oils, greases and fluids changed as per spec, The rust side is a different matter, all the visible parts of the car, outside, inside and underside, usually speak for them selves, with regard to rust, most of the usual 'rust traps' on the 100 can be accessed fairly easily, I.E inner rear wings/wheel arches, you can see a good amount by just removing the rear lights then a look see with a good torch, if there is just a build up of mud for instance, it can be washed out with a hose pipe,It's a 1999 reg and has 92,000 miles on it not even run in by Toyota LC standards
You aint gona get any 80 or 100 for much less than £5000, even that 1999 at £7,500 is a good price presuming everything checks out.Thanks for the comments guys, will do an mot history check soon see what that shows up.
Once I've sold my BMW I will have around £11,000 so might wait for a better one after the lockdown.
The one in the pics is £7,500
Most of that is scaremongering just to drum up business for the garage, I take mine to the local council MOT testing station, they don't do repairs for the public so are not intrested in silly advisories, just honest advice. FYI, you can find you local council MOT testing station on Google.This is it's most recently done not, the others do not read to good with little things I would never take to an mot without sorting first.View attachment 165408