I use a Laptop for a Cpu Mining worker, I get about ~2-3kh/s from this Laptop old Pentium Duo Core. I dont have it tweaked to max hash rate to prevent over heating, I also use a laptop chiller.
Between 3 pc's and a laptop I mine at ~23khs, yes it is not much at all but Im still grinding away. If you want to mine go ahead and get started use what you have. Low hash rate shouldnt discourage you, it just takes alot longer.
I would try it only at work computer.
Because I paying both, laptop purchase & elecricity bills with hard earned money, i wouldnt try it at home.
But then, lucky childs who thinks all is free