A 97 V8 for $20k? Either a hell of a deal or a money pit. Broken V8s are not cheap or easy to fix, much more risk than the 4cyl.
Our goal is restoration/rebuild. A restored car with 80,000 miles may be better than a good car with 40,000 miles. Odds are that the 40 k mile car will need a lot over the next 3 years like fuel tanks, water pump, timing belt, clutch, hoses etc. then after 3 years you have a well maintained car with a leaky tired engine, and a bunch of repairs. If you are strictly a weekend driver then the car may still be pretty good with low miles, but if you drive it a lot it will need stuff. and if you don't drive it it will need stuff.
Sure there are no guarantees or warranties, but chances are the rebuilt car is going to be fairly reliable, and have a lot less repairs and be in better condition 3 years from now.
Check out 'Toms 89 project' thread to see the kind of stuff we do.
So the 94 S4 is excellent mechanically, being all rebuilt, and has a very nice interior. The only issue is the paint is only pretty good and it has a few gel coat cracks. It doesn't need a respray, but it would if you want a pristine car, although a good paint guy could do a partial respray and it would look very nice.
That S4 in TX has a lot of upgrades by John Welch who is a good performance guy, it could be a good car IF not abused and maintained. The problem is you won't know the motor.
BTW those of you hunting used Esprits, I would highly recommend compression testing before you buy