Lindsey, this is the risk we are willing to accept when we decide to host new dogs from different families at the same time. Since you have no dogs of your own, and you can't really do meet&greet, there is no way of telling if the dog will be aggressive or not.

Dog might show you behavior that owners have never seen before due to new environment and stress. Some owners never socialize their dog, and do not lie to you when say that their dog never bitten anyone.

As a safe practice, keep new dogs separated until they become absolutely familiar with each other. Take them on long, stringent walks, to a complete exhaustion. Tired dog never fights, walking together builds pack spirit, returning after a really long walk resets home as a "neutral" territory.

I generally try to avoid having two new dogs from different families at the same time. Only after I had hosted each one of them before, and know that they are a good fit, I book them together. Otherwise you will have an injured pet, and unhappy parents.

Best way yet, rescue a dog and take him to meet&greets. Having your own dog makes sitting so much more easier and enjoyable.

Invisible fence is effective, but expensive tool. It should be your last resort, because your beagle simply needs enough exercise, and fence does not address that. It only deals with the side effects. It is understandable that not everyone can provide daily exercise , thus invisible fence might be the right solution to your problem. To those who say it is cruel, I say that being a little tough with your dog beats having it run over by a car. Invisible fence provides solid results, while those who judge it for cruelness fail to provide any alternatively effective solutions.

Your dog needs to be exhausted on a daily basis, given a job to do. If you can't provide that at the moment, invisible fence will keep it contained.

More information is required to determine what might cause it. Does it happen aggressively or playful? Does it happen whenever you walk, or only when you walk past your dog? Definitely do not use squirt bottle. Either your dog had a dramatic episode in the past or is not getting proper exercise. Like Amberlie R. mentioned, herding dogs do bite at the feet of the sheep.

More information is required to determine what might cause it. Does it happen aggressively or playful? Does it happen whenever you walk, or only when you walk past your dog? Definitely do not use squirt bottle. Either your dog is not getting proper exercise or had a dramatic episode in the past.