Weird idle

i'm looking at buying this 93 civic hatch with a 00 b16 (usdm) motor in it. I test drove it and when it would idle it would like rev up and down. what's wrong with it? and is this bad?

It's Bad, if you consider having a car problem, a Problem.

it could be a few things....depending , what all was done to the vehicle, is it JUST a swap ? or are they other mods here and there ??

It must be your Idle Air Control Valve.