How Long Can A Dog Be Home Alone?

I want to adopt an older dog from the pound. Not a bull breed. It needs to be a small dog. Maybe 2-3 years, not a puppy. I work, like most people, so Im out from around 8:30 until 3:00. I don’t understand how people on here say you cant have a dog unless your home all day! Don’t people work and have dogs?? I don’t want to adopt like a 10 year old, because I adopted an older cat who I could only love for 4 years, then she had to be put down because she had cancer. So is there a breed of dog that can stay home for around maybe 7-8 hours a day? Would crate training be a good idea? Or would it be better to have it in the house, with a dog flap so it can go into the garden. Help? I did those dog breed quizzes and the border terrier came up 4 times, and other times I got things like the greyhound and Chihuahua. It must be good with cats, as I have a cat, and if they get along they might start liking eachother. This will be my first dog, and I really want something small, I dont want anything heavyer than around 20 lb. Thanks

Do Greyhounds Like To Go For Long Runs, Such As Training For Marathons With Their Owners, Or Only Shorter Runs?

I like what greyhounds look like and the idea of saving a dog. I like to run long distances. Do greyhounds like to run long distances with their owners or just shorter distances? How far do they like to run each day? I can’t have one right now but when I get to the right place and time, I would really like to look into having one or two greyhounds.