We are very interested in the buy and hold rental model.  

The house was completely re-modeled upon purchase and in a way that made renting out the bottom seamless: 1,600 SQFT up and 1,600 SQFT bottom, BOTH having 3bd/2ba, each having FULL range kitchens, laundry rooms, living/family rooms, dining rooms, completely separate entrances (walk-out basement accessed around side yard), and bifurcated parking spots.  

I guess that depends on your business model and goals.

Zillow is, as others have stated, a business model based on getting you to their free site in order to derive profits later via other means. 

Occasionally.My business model is 95% referral based.

I have recently become very interested in the wholesale/ flip business model as I am a licensed realtor in Texas.I came across my first wholesale deal this week but I want some assistance as to what would be the best way to handle this transaction.

@Andrew Auger nice model.

Also, I would factor all of the future maintenance with a PM or contractor in the cost model. 

This is a fact that we all have to deal with, however I wouldn't put too much emphasis on it in regards to your business model.

He never set foot in the apartment (saw a model) because when he looked at it the tenants were still there and it wasn't going to be available until the day he moved in.