I'm also very skeptical of the 'engine rebuilt by Volvo' claim. These engines are pretty tough and without performance mods they will go a long time even without perfect maintenance. Unless it was rebuilt because of a broken timing belt which was not changed on time? If that's the case I would want some serious testing before I trusted that the engine was really holding together properly (compression, leak-down).

Just because it doesn't have a MIL right now doesn't mean it won't light up with a week of driving.

The AWD system is pretty solid. Fluid flushes are always recommended. Bevel gear, rear diff, and the haldex fluid can all be changed, and should be.

AFAIK the trans is indeed an Aisin, prob the 5-speed IIRC. If so you need 3309/Toyota-IV fluid. Fluid should be be bright red with no black/brown flecks/streaking when wiped with clean bright white paper. It probably isn't and you should negotiate on price with this.

The XC90 is not as useful as the XC70 unless you need 7-pass seating or class-III towing, which your candidate may or may not be rated for. They're nice for sure, but they have less usable interior room and get much worse mileage. They're a solid platform in general though, which is a main reason Volvo hasn't updated the thing in a DECADE.

The suspension should be pretty tough compared to the lighter on-road models, and Volvo's braking stuff is usually pretty solid too. As with any new car you'll want to flush all the fluids including the brake fluid.

Happy hunting!
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1998 V70 AWD->FWD->AWD Turbo 215k+