Here's what you can typically expect for your money when shopping for a '91 (leaving aside the question of aftermarket modifications, which can cause the value to go up OR down):
$35-40K - super low mileage (under 20K, with those under 10K towards the top of this range), five-speed, clean title, perfect condition, no accidents
$32-35K - moderate mileage (20-60K), five-speed, clean title, well maintained, excellent condition, no accidents or minor accidents properly repaired and not visible
$30-32K - moderately high mileage (60-90K), five speed, clean title, well maintained, very good condition but minor scratches and chips and a few small mechanical problems, minor accidents properly repaired and not visible
$27-30K - high mileage (over 100K) or automatic transmission, clean title, most maintenance done but not timing belt and water pump, fair condition with several major items requiring repair, minor accidents possibly visible
$25-27K - at least two of the following conditions: very high mileage (over 150K miles), salvage or theft title, major systems not operational with expensive repairs required, major accident history with body damage readily apparent
$23-25K - all of the following conditions: very high mileage (over 150K miles), salvage or theft title, major systems not operational with expensive repairs required, major accident history with body damage readily apparent
Your description of "not really beat up" sounds like a car in the $27-32K categories. You're expecting to pay $20K for it. Forget it.