If the price is right for the area, then determine the quality of the cash flow: is the building under-performing?  

@Ross GillYou may want to look into a Master Lease Option strategya. find a mom and pop "poorly performing" apartment buildingb. offer the low "NOI" as an option to purchase pricec.

So is it kind of a % type deal or more a flat rate depending on how well the bird dog performs. 

Of course, easier landlording and likely less potential variability in performance also than the former two.

For $150/ft in rehab, I would think it would have to have very high-end finishes.. travertine, custom amazing cabinets, some viking appliances etc.But I've also heard people that do their own work say "there was $200K in rehab performed".

Isaac you need to wait for a "burn in" period and do nothing.Watch how the tenants perform and the property runs before making any huge capital decisions.Yes we look at those items before purchasing to see the best strategy but since you have already closed it is best to do some more research.

How is it performing?

Perform sweat equity.

What was the overall cost per form filled out?

Clearly, in your specific case, the seller performed DD and fond you to be more than credit worthy, this a feeling of comfort.