Other posters have covered it pretty well (no pun intended), but I'd
like to add, having just sold a house in NY state: the federal HUD
guideline states that 5gpm sustained flow over a 4 hour period is
adequate for a 1 or 2 family dwelling.

Jim also had a good point with the pockets of water. Our well had a
lot of dissolved iron and other hard minerals, while the neighbors did
not. All were drilled. One other neighbor drilled 3 wells and hit
salt water pockets in every one (this was near Syracuse, nowhere near
any sal****er bodies). My point is that there is a lot of variation in
the water table and the surrounding geological conditions.