1921 Liberty Half Fake?

I would be suspicious. The 9 in the date stands out since the stem seems too short. It should extend to below the left edge of the upper loop of the 9 while on this coin it ends well before it gets below that point. The center of the coin looks odd, as if Miss Liberty has put on some excess weight at the hip. The grade would appear to be in the AU range and the coin (if genuine) is worth $2000 or so. Having it certified by ANACS, NGC, or PCGS to confirm authenticity should be mandatory. See below for a photo of a genuine 1921-P graded as AU-50 by PCGS (from the Heritage website).

If the coin seems OK after close examination I would require a written guarantee of authenticity, to be confirmed by professional grading (at your expense) after you buy it.

That's a great observation with regards to the 9. I checked out the 2 to but didn't think too much about the other numbers.
I think that might be the key giveaway as it seems evident that the lower loop doesn't even come close to the left edge of the upper loop.
This however begs the question whether or not the date was uniformly struck for this year, but something tells me when I see the coin, I'll for sure if its a fake by weighting it. It just worries me that the overall appearance of the coin in the picture seems to be unlike other 1921 P half dollars

The flowing scarf tips to the left of the obverse are also not the same as Jaobler's. Check out the end flips of the scarf (top & bottom) and the little scarf tip that comes directly from the body.

I say fake.

Sorry.

how much does he want for it?

This oldtimer casts a vote for this one being a fake. Note that the last one in the date is somewhat high. That's probably so that other 1920's dates can be more easily produced. I've seen these before; the last time being at a flea market outside Youngstown, Ohio. The dealer had both a P+D; same look and grade as this one. To his credit, he was savvy and honest, having them on display for collectors to be wary. I bought some real coins from him that day ... good deals, and my way of giving him a pat on the back.

One method of peddling these copies is to put them in an album or in a page, alongside legitimate coins. Seeing this, the buyer is more likely to believe that he's getting a deal when, in reality, he's the one getting hooked.

I haven't heard anything about a price here yet. That too might be tip off that the seller knows if real or not. I noticed you said someone in your area and not someone you know. When it comes to buying or selling coins you should be carefull of who you talk to and/or mention you collect coins in your area if you do not really know them. Maybe not in this case but someone pretending to be from your area and selling coins could also be trying to find out who has a coin collection. So you don't buy this one but he now knows you and that you collect coins.
Of course my statements of those situations are based on the area I live where crime runs rampant. By me everyone plays like they are broke, have nothing of value, can't afford anything, etc.
Better to be safe than sorry.

Fake!