Cats are harmless a big dog maybe but if they pay a deposit. 

For example, if a tenant has a dog that is not allowed in the lease are you required by law to give them a warning to remove the dog, or are you able to just go straight into the eviction process and just send them the papers?

Two exterior doorknobs have huge dents and are misshapen from her dog - they technically work, but look like cr*p.

. ;-) @Casey Jarratt, I will also send bird dogs down to the courthouse records room to pull the fresh ones as they come in.Seize the day!

The odor in the garage was unbearable with dog urine and mouse feces.

I have moved toward requiring full security deposit and 1st months rent in a money order (and dog deposit) if it applies at the lease signing.

Is paying a bird dog commission based on the purchase of real estate illegal?

Sounds to me like an experienced investor dumping a dog on you and taking a large down payment to make it painful for you to walk once you are trapped owning this thing.

should a bird dogger have his/her investor sign a contract or a real estate bird dog agreement

I was trying to bird dog wholesale deals for my former business coach, but all he did was deliver promises with no results (he was more involved in multi-level marketing more than REI).