My friend is looking at a turbo Legacy. Here is the problem. The battery had died on it and when the guy replaced the battery, he switched the terminals. He blew the fuse in the fuse box and replaced it with a jumper wire. He said it cranks now but doesn't turn over. What's wrong and what is needed to fix it. Thanks.

Brent

So did the owner do this or a shop/mechanic? It is extremely dangerous to replace a fuse with a jumper and no truly competent mechanic would ever do this. Not to mention that he connected the battery backwards.
First thing that must be done is replace that jumper with the proper rating fuse. Next, check all of the fuses in the car in both fuse boxes (I assume the Legacy has the two fuse boxes, one under the hood and one under the dash). If no more fuses are blown it is possible that the ECU and/or other electrical/electronic devices in the car were damaged by the reverse polarity and need to be replaced.
I would suggest that your friend walk away from this car now, no matter how tempting it may be. Between this problem and who knows what other abuse it may have suffered at the hands of this person he doesn't want it.
I know these are somewhat rare cars but he needs to keep looking, this isn't the one.
The only way this car should still be considered is if it is very, very cheap and your friend is willing to take a chance on it being a "science project" rather than a turn-key driver.