Pets for rental property

[Maneesh Joshi]

Hello All, I am considering allowing dogs for my rental property in Philadelphia.  Even though I am hesitant to do so I feel like it will open up the tenant pool.  I am planning on having discretion on what types of dogs I will allow.  What is everyone's experience with allowing dogs?  Are there particular ones you wont allow(big, small, certain breeds)? 

Also, do you find it better to have an upfront pet fee or a monthly pet rent?

Thanks In advance!