I bought a 928 S4 in Germany in the 1980’s and brought it back to the US. To answer your questions:
if this car will suit a first time driver? NO
Is this car gas friendly? NO
Is it expensive to repair? YES
What is a fair price for a used one? FREE
How reliable is the car? NOT AT ALL
Consider the purchase price to be a down payment. Corrected for inflation, a 928 cost about $75,000 new. Now, it’s a $5,000 used car. However, it is still a $75,000 car to maintain and fix. Parts and labor have not depreciated as did the car.
Get him a nice clean Honda or Toyota.