Open your eyes.
This group knows what they say.
I have flown several 20 series Lears as well as 35's, 55's, and the 60's.
Of all the Learjets, the 20 series is the most difficult of them all to handle. Definately not for the unexperienced flight crew. It would be wise, if your owners are set on this type, to fly with an experienced flight crew for a couple hundred hours minimum.
It is a very unforgiving airplane, and must be watched constantly. High Ref speeds and a handful on a missed approach. 3 hour airplane, 300 pounds burn on taxi to departure. But....
One of the best peforming Lears to date. A real kick in the pants to fly.
The RVSM is a real issue, and should not be overlooked in your purchase.
It is unlikely that this plane will have any future value outside of a boat anchore within a year if Learjet or an outside group dosen't put forward the engineering to get the 30 year old hulls RVSM'd for $150,000 or less, (which is highly unlikely).
If your looking for a Learjet look at a 30 series (31 or 35). RVSM approved due to air data computers and auto pilot. The 60's are a bargin in the market at the moment and a real pleasure to fly as well as the 55's.
Good Luck