Your screening isn't hard. It's responsible. Aggressive breeds are a liability to you as a landlord. Your home insurance company may require you to take a higher policy or may deny you insurance for having certain breeds on the property. That being said, not all pitbulls, rotwielers, etc are dangerous. It depends on how they are raised and socialized. If you have a no pet/dog policy, you may want to amend it to allow for small breeds providing they are well behaved, with references from a vet and a pet deposit. Multiple families in a sfh is potentially a violation of health and safety codes for which you would be held liable. A credit score of 600 is considered an ok or average score. Below that, you are inviting a person with a proven track record of lateness or non-payment.