SWAP PETS

My cousin wants two pet mice, and I’m trying to help him and his Mother gather information. (We all know that she’ll end up taking care of them, anyway.) I am unable to find much about price range for feed mice (or fancy mice) online (Outside of independent retailers and independent breeders. I’m thinking more petco/petsmart, as to where the mice will be purchased.), and can’t find anywhere locally to check prices, so that information is vital.

Thanks in advance.
We were considering a rat, but he’s afraid of animals bigger than his feet. I’m not quite sure why. Plus, it would become lonely, so his mother would have to buy two, and then she’d have to buy a bigger cage, and with limited funds, it wouldn’t be a very logical decision on a financial level. It’ll also be his first pet(s), so we want to find something he can love for awhile, become attatched to, and start to understand death as much as his mind lets him once it passes. Thank you both (excluding the moron who posted before you two, of course.) for answering honestly.