Right of the bat, I don't know if you can do that legally. I would say no, but that's only from the "better safe than sorry" perspective.
Now, that said, here's some food for thought, if you're inclined.....
You've got tunnel vision and you're missing the big picture. (IMHO)
Say you found a handgun at a fair price. But you still have to factor in FFL fees as well as shipping. Also, will your FFL even agree to letting you store it there for 2 months. Hell I don't want my stuff lying around for more than 2 hours, let alone 2 months. Who knows what can happen in that time. Also, with online sales, they're typically an "all sales final" deal. So if it's scratched, missing the front sight (don't ask), or for some reason isn't too your liking or satisfaction, you're usually stuck with it. Plus, some warranties require registration within 30 days, but that's from the date of purchase, not from date of pick up.
When you buy from a store, if you don't like the one they bring out, you can simply ask "do you have any more of these? " and they'll bring more to choose from. Me, I'm picky with anything I buy. Machine marks, swirl marks, any rub marks from the box, even unlucky serial numbers with to many 4's or a 666 or something. In a store you can always walk away. If you buy locally you can also take it home and register your product for warranty immediately. And of course the added bonus of keeping the money in PA, helping your local dealer out in this otherwise inhospitable market.
That is of course overlooking the obvious. A handgun should typically be handled before you decide to buy it. Glocks fit perfectly in my hands, other folks hate them. Some folks think Xd feels better. M&P better yet. I love my M9, my wife thinks it's too big. You can do all the homework you want online deciding what the best gun is, but if it feels like crap in your hand, and/or doesn't "point" naturally, you may end up really disliking it, to the point you'll either sell it, trade it or simply buy something else, and in all 3 scenarios you actually end up losing more that what you saved by buying online.
Just my opinion, which is worth what you paid for it.