Care to elaborate? I'm not sure of the size, but there are 100.000+ related monthly searches on Google (under $.20 per click), which is how I hope to reach customers.
I guess that depends on the specialisation (see other thread in this post). Maybe something like "software decision help", "scientific research service", "professional math help", "software evaluation", "Matlab debugging"...
It's a pretty bad and unscalable idea. Don't follow it. It won't work. 100.000 searches is nothing, start breaking it down to how many are willing to pay, and you see how small the market is. Unless you have an extra-ordinary passion for this area, find something more immediately lucrative.
You'll discover that there is a problem.