It's completely impossible to know. "buy viagra without a prescription" or even "buy viagra in new jersey" are definitely longtail. But if you think you're going to rank for em with 5 blog comments and a couple directory submissions, you're in for a rude awakening. Comparatively, "the name of the black dude on scrubs" or "how fast does my fan spin" you would rank a lot higher with the same backlinks. If you don't want to say your niche(understandably), it's impossible to tell. And even if you did, chances are it would be very difficult to estimate.
Oh yeah, and it depends how much link juice the sites on those "ips" can pass.
And about a million other factors.
If you don't like that answer, the answer is 42.
