Hi there. If you havent figured it out yet, I'm pretty new here.

Anyway, I have these four Lykos pups; each are 2 Hero Generations (or whatever it's called). 3/4 have tireless heart, one is pearl, two are grey, one is brown. 

Here's links to each: 

http://beastkeeper.com/pet/845039

http://beastkeeper.com/pet/845086

http://beastkeeper.com/pet/846060

http://beastkeeper.com/pet/846546

I was considering leveling them up and selling them, but I want to know what  decent price would be for them in general; a pet prices guide would be useful too, if that exists? 

Thanks! 

There's no pricing guide. Prices fluxuate a lot depending on who's buying at any given time, whether there's an event going on, etc. If I were you I'd go to the Pet Trades and look at the prices of comparable pets (e.g. GP2 lykos with a few good genes), and price them similarly.