First of all I have no idea why anyone would be interested in a hail damaged car unless it is extremely cheap. This one isn't even close. What you need to do is get an estimate for the repairs. Hail damage can be expensive if it is as bad as you say it is. Whoever owned this car got paid up front for the damage and now they are asking you to pay again.
Don't do it. Let the seller carry the burden of the damage.
In rough condition ( based on the severe hail damage) that car is worth in the area of $9500. Even if the car was in good condition $15,000 is way over priced.
