How big is the advantage/disadvantage associated with a player's preference to proximity?  For example, if I'm interested in a kid who's right next door, but he prefers "Far From Home," does this put me at a big disadvantage to someone further away?

Also, does anyone know the range that "Close to Home" and "Far From Home" applies to?

I don't think it is very much

I wouldn't consider proximity a factor in deciding who to recruit at all. The impact is minimal. According to some estimates, it is roughly close to the cost of one home visit. The breakpoint for home/far away is 300 miles.

I actually think the far from home preference is pretty significant. The close to home not so much.

Does anyone know the answer to this question - in other words if I am 400 miles away from a prospect that wants to go far from home, and a school that is 20 miles from him is competing with me, how much of an advantage do  I have?

Bumping

Curious if anyone has an answer to this a year later. How much of an impact does it have in recruiting?

I don't know the answer, BUT, I never even look at that while recruiting.  I don't think the impact is very much at all.  I guess at the Div-3 level, where there is much less cash involved in recruiting, it might have a barely noticeable impact, I think it has no noticeable impact above that.

The impact is pretty much irrelevant. It is also not constant, so the extent of the effect would on distances involved in the specific circumstance. If a kid wants to be "far from" home, he'll be more enamored by a school 900 miles away than he will be with a school 600 miles away. Similarly a kid that wants to be "close to home" will prefer a school 20 miles from his home more than a school 160. (Both schools in both scenario would receive a boost over someone who wasn't far/close, but the boost isn't the same for both). 

Aside from a case where two teams jump on the kid with an el cheapo special and have no more money to throw at the kid, I really can't envision a scenario where the effect comes into play. It's one of those factors of the game that I don't give passing thought to during the active recruiting phase. As someone said above, one HV probably overpowers even the most extreme level of the effect, whatever it is.