If I recently find a stray dog and want to keep it as mine how much will it cost to register it if it's already an adult?

This varies according to what city you live in. The cost of a pet license is usually under $20. There is usually a discounted price if you have proof that the dog was spayed or neutered. You will also need proof of vaccinations, so you have to that first.

Did you put up found dog ads everywhere? Did you go to the vet and check for microchip? You have to wait a week before you can legally adopt the dog from the shelter. If no one claims him/her within the week, you can adopt it.

What kind of register? AKC? Any kennel club? Most likely it's a mutt. So you can't register a mutt with any kennel club, unless it was a fake kennel club that allows mutts.

If you recently found a stray you MUST, by law, turn them over to animal control so their owners have a chance to find them and be reunited with them. Then after the holding period you may ADOPT THEM. And then you can ask that question. So please lose the 4 year old mentality of "finder's keepers, losers weepers" because for all you know they could be microchipped and can be given back to their family. It's something called putting yourself in some one else's shoes so stop and think how YOU'D feel if somebody just decided to keep your pet. YOU'D HATE IT AND BE REALLY P*SSED OFF because they were being so selfish.

Depends on where you live. I would turn it over to the shelter and then legally adopt it (tell them you'd like to adopt it when you turn it in). They will take care of providing preliminary vaccinations and you will pay them for the adoption and registration of the dog.

Should this be someone's dog (lost or stolen or something else) and you don't legally adopt it then you could get in trouble with the law. If you turn it in, no one claims it, and then you adopt it the dog will 100% be yours.