Please tell me he didn't buy that Sundance that was, depending on when you saw the ads either a Roadrunner or a Sebring Plus, for sale in the Jacksonville/Orange Park area. That car was for sale for a long time.
Carcrazyguy is right about rarity and value. The Sundance is much more rare than the Road Runners, but I've never seen any demand for them. Most folks have never heard of them, or vaguely recall them, and aren't very interested in them when they get educated on them. Plus that interior seems cool at first because it's different, but that novelty wear off fast.
If this car is the one I'm thinking about, it was way overpriced. It was at a high of around $6,500, and I think the last ad I saw was $4,500. I would have put a value of no more than $2,000 on it myself. The interior on it looked decent, but if he's going to restore it he's going to need to clean up or replace it, and being white that can be a challenge. They repop the stripes and logo decals, but I don't know if they repop the seat covers, and those covers are pretty faded.
Going the Road Runner clone route is a little easier, but the car has some drawbacks. First, you'll need to replace the seat covers, door panels, and inner quarter panel panels if you want to get rid of that Sante Fe-look stuff, so that'll be around $500 and up. The second drawback is the car is a bench seat/column shifter model and not a buckets/console which would sell better. And lastly he's got a 318 in there and 318 cars better have lots of tangible cool factor components like a perfect body, bucket/console interior, etc. if they're going to sell.
Lastly, to arsinist01's point, the market for these cars is very soft. I saw a nice 73 road runner selling in Middleburg for almost a year at $5,500, and another down by Ocala that one that was around $7,500, and that car still pops up for sale every now and again. Unless he changes the car to a 340/360 car, or even better a big block, and changes it to a bucket/console car, he's probably looking at the car selling for $5,000-$6,000 provided he invests in a decent paint job.