I have two small dogs that don't shed a lot, but sometimes they still make other messes. They puke now and then.
One of my guys is an excited pee'er, so when a new person comes over and greets him he pees all over the place. Sometimes they get sick or their stomachs get upset for whatever reason, and they have accidents. They can't help it. I guess I don't give it too much thought normally, but they do require a lot of time. A lot of time playing with them, feeding them, taking them outside, trips to the vet, etc. I sometimes feel I spend hours a day waiting outside with them to do their business! I think the only way you could make it work being away for 12 hours consistently is if you had someone to come let him out at the half way point- either someone you know or someone you hire to come over and walk the dog. Or take the dog to doggie day care. 12 hours is just way too long. I feel guilty for the time I'm away and it's not as long as that. Most people have to work and most dogs adapt just fine. But 12 hours is a stretch at a time IMO.
And they can get expensive as well especially if they get sick. Food, toys, nail trims, routine vet visits, heartworm medicine, it all adds up and as I said if the dog gets sick it can turn into 1,000's of dollars in a short time. I have some single friends who would love to have a dog, but they just aren't willing to adapt their life to make the time for one and there's nothing wrong with that. It's not for everyone. But I wouldn't trade my dogs for anything in the world. They are worth all of it and it doesn't even feel like work to me because I love them and I'm happy to do the things they need.