Would you take in a small aggressive dog again?

I personally would, but that is because I actually advertise for the market of people who have very difficult dogs, and I have the experience to deal with such a situation.

If you are uncomfortable with it, and especially if you have multiple clients dogs at your home at one time then I would be honest with the owner. A simple message that says "thank you so much for trusting me to care for "dogs name" while you were away, unfortunately it turns out that in my home she was much more aggressive than we both first thought and due to the safety of my dog and other clients dogs who are in my home every day I will not be able to care for "dogs name" again in the future, I wish you the best in finding someone who is a better fit for your pups specific needs"

I agree with Deb. If you are watching dogs from different families, safety of those pups has to be the top priority. If you think you are capable of handling her with your own dog by keeping them separate, tell the owner that you are more than willing to sit her dog again, but she would have to pay extra to have the dog be the only one on the stay. Even just incessant barking can be extremely stressful to other guest dogs. This surcharge rarely is agreeable to the owner, but shows you're willing to make it work.

And if/when they do not agree to that, you can graciously just let them know that because you have seen their dog exhibit aggressive behavior and resource guarding, you cannot risk their being an incident that gets out of hand. This is good for their dog also, as her aggression might trigger reactivity in another dog.

To remedy the whole thing, give the owner some advice on finding the best fit for their pup. Look for sitters that sit only one dog at a time, and maybe don't have any pets of their own. You can also offer to reach out to the referral network via Facebook, and send them the Rover Match information to get professional assistance in finding a good fit.

NO. I don't hesitate to tell an owner if they have an aggressive/dangerous dog that needs to find another sitter. Of course I try to do it graciously, or as graciously as possible when you're telling someone they have an unmanageable monster.