Well, really. I bought a bunch of food thinking that was required to feed my pets, but apparently that wasn't so. So I spent all my cash on this purchase, still have a yellow bar on my active pets, and cannot pay for healing them anymore. Are there any ways to earn money aside from the missions (which would still mean I have to wait an hour, at least) that can be done with low-health pets? :S I feel.... stuck.

Your pets gain health over time, so you can just let your pets sit for awhile and do something else, then start playing again.

You can take this time to allocate stat points accordingly to your pets. You should also read up on some guides to start building your pets to have HP or strengths so they're better in battle (check the forum for Guides).