No he has not gotten into any trash or eaten anything that is not dog food. To keep you updated he has eaten today and is becoming less lethargic. He is now wagging his tail and walking around a lot more.
As Shannon781 stated, most vets offices offer Care Credit for people who don't have the money to pay their entire bill off all at once.
With regard to your dog, you need to get him in to be seen by a vet ASAP. There is obviously something wrong if he is lethargic and won't eat, and at the age of 11, and being a mix of large breeds, he is considered to be quite elderly. When they are up in years like that, things can happen quickly and what might be considered to be something very minor in a young dog can cause a dog to go south rapidly when they are aged. Most vets offices are open until noon on Saturday, so I would get him in there no later than first thing in the morning, and it would actually be preferrable to take him to an emergency vet TONIGHT and not make him wait until tomorrow morning.
Please post back and let us know how he is.
Ghilly
A lot of vets offer Care Credit where you can get interest free credit for 1-2 years. Does the dog get into the garbage or eat anything it wasn't suppose to lately? He needs to be checked out, it could be serious.