The group we adopted our greyhounds through have some people who watch dogs for a living. We've used a couple of them and have had excellent results. We have no hesitations at all leaving them and they seem to enjoy it. They get to live in someones home, socialize with other greyhounds and get walked/fed as we do.

Any possibility the group you got your dog through has contacts with people who do it for a living? We went and met the people, introduced the dogs, saw their home, etc before committing.