Most will be a standard E26 (Edison type, 26mm) screw in base for the bulb, but in some areas, such as here in California, all of the new construction housings must have a 2 pin connector so that you cannot install a regular screw type bulb into the housing, instead you have to use a high efficiency bulb with a 2 pin plug.

The big help now is that technology is leaps and bounds better than it was 20 years ago and helps your efficiency beyond anything else.

On our future projects, I am sure there are ways to become more efficient as far as profitability.

If there's a way to take an analysis all the way down to zip codes (or smaller) efficiently, without having to first identify a market to look in, I'm all ears. 

It is just efficient. 

Mistake #2: didn't research enough on how bank internal efficiencies can prolong short sales.- Very short closing period.

You really want seller financing on this ( there is a good chance you won't get a lender to finance) and it can be an efficient use to do it all cash if you have that option .Its also a large vacancy factor so you will have to have capital and a plan to get the lots filled.  

One of the best local contractors told me he wouldn't warranty it and relocating it was best since new machines are so efficient they'll shut off w/out proper airflow.

At what point does it become more productive and efficient......or does it ever?

At the end of the day, this might price out like clipping coupons, ie, its an efficient use of your time if you make around $10 per hour.