losing hair on ears

Hey guys, I've noticed over the past week that my cat has been loosing a little bit of hair around the back of her ears near the base. Could this be ear mites, ring worm, or something else (Like from my dog playing with her). I'm not sure if I should take her to the vet for this because I'm doing an internship that's unpaid right now so I'm a little tight on money. I'm going to go take a picture and I'll post it so you guys may be able to help me out.

Sorry if these are really big.

Is he scratching at them a lot? If so, he may have mites or an infection.

That's the weird thing. I haven't really been noticing her scratching at her ears excessively.

Could be a number of things. Mites, fleas, infection, allergies, allergic reaction... If you don't plan to take her to a vet right away, keep a close eye on her, monitor the area for any signs that it's getting worse, scratching, etc. and definitely take her if it spreads or she is scratching a lot.