Nope, dogs are never too old to learn new tricks. I adopted Kaedyn at age 5/6. He didn't know a single command and actually was aggressive (this was only back in September). He's pretty obedient now. He has a better recall than my youngster, knows all his basic commands and is preparing for advance obedience. And most of the training was actually done by me. Trainers are just there to teach clients how to teach their dogs. You don't need any money to train your dog. I'm sure you could find some excellent training articles online (or a few good books from your library). There are also more experienced people here that might give you a few pointers.

Is there an area (inside) you could confine her to while you're not home? Or even a dog run outside would work nicely. A crate may work as well, although I'm not a fan of crating for more than a couple hours.