i create an avs site with a tour that is the quality of the paysite tour i would make and send it some traffic that is very specific using galleries or google or something that tells the surfers about where they're going.

then you'll know about the popularity of the niche even if your tour misses the mark (after all, it is a niche you haven't worked before). even if you miss with the tour, you can see if the hits pour in or trickle. if they pour in without sales, it's worth trying a new tour.