Confused..

Just came back from a week long business trip, my father watched my calico for me and a day prior to returning he called and said something was wrong with my Julie's upper front arm.
So I come home and there's not only a patch of fur missing, but it's circular and is quite raw. Was wondering if anyone knew of this was some sort of infection?
My cat does go outside occasionally but she doesn't stray far, and I've yet to see any stray cats myself so I'm unsure. Wanted to ask before I hit a vet due to lack of funds due to a tight ship.
Thanks!!

I honestly, say..Vet... that looks like it is sore and can easily get infected. 

I really do not know what it is..

Please do not hesitate going to the Vet..

Thanks for your input. I plan to after today, but in the mean time im trying to get imput and see if it might just be a little fight from a possbile catfight? Or if its something super serious. My father said she was limping for about 2 days but now shes walking fine.

That's an open wound.  I'm glad you're taking her to the vet.  So many things can happen to them outdoors, there's no way of knowing what did this, but she needs help.  I'm sure it's painful.  Best of luck!

Looks like an abscess that's ruptured. She probably got bit by another cat, the bite got infected, the abscess filled with pus, and for whatever reason it ruptured just now. You'll need to flush it daily with disinfectant solution prescribed by your vet and you may want to do a round of antibiotics too. Most likely the vet will give you a cone to keep her from licking it. Definitely something you need to see the vet for though. Good luck!