Other than that, the tenants behave well.A repair person will cost $150 just to show up.

Note, if you choose not to do this, you are NOT behaving unethically or illegally.

We state in our lease that we must approve any new roommates and we must be notified if you will be having a guest stay for more than 7 days.

The difference is trained animals are better behaved than most tenants.

If the dog in question is a pit bull and is objectively well behaved with zero history of aggression, I don't think that it is safe to assume, as you say, that you can reject based on your personal and subjective fear of pit bulls, or even dogs in general. 

If I have a prohibited conduct clause in my lease which states that "the tenant cannot disturb, threaten the comfort, health or rights of others" can I use this as a basis for an eviction if the tenants animal lunged at or attacked someone with the assumption that there is no prior history of the animal behaving in a threatening manner.

Nor am I saying that all men (or all women) behave in certain ways. 

It could give you another tool in your tool belt to potentially find more deals or help agents sell homes that they may be having a hard time selling.Reach out if I can help further!

This is the thought you should be having. 

This is the part I'm not wired for, but the reality is this is the way it needs to be. Having