The pre-flips were as I expected, total horror shows (ceilings falling in and feces on the floor, pit bulls loose in the back, etc.).

It needs a new ceiling and new carpet.

New floors are needed, plus a repaint and popcorn ceiling removal.

Especially the days when you discover that big capex like a roof being blow off (happened 2 years ago), some tweakers climbed up on the roof and gutted the A/C (did two of those in the last 12 months), an evap cooler leaked for so long that the drywall on the ceiling of the kids bedroom caved in (last year), the hot water heater blew a hose and a major leak went unnoticed for 10 hours flooding the hall, kitchen and living room (dealing with that now), the tenant smelled gas outside, the gas company came and shut off the gas because the underground pipe is corroded AND also discovered that the water heater is not venting properly so it got red tagged (just dealt with that last month) or the time the tenant "invited" a homeless guy over, he moved in, then called his other homeless buddy up and he parked his crappy RV with his entire family living in it in the driveway.

For example, we will need 16 ceiling fans and I'm wondering if that quantity can be purchased at a discount, and if so, where?  

There is generally a floor and a ceiling on price per square foot, in any given area, and $20-30k for a couple hundred more SF might absolutely be right depending on the local market.

We don't hear all of the sleepless nights staring at the ceiling when your money is held up in a deal and you aren't sure how it is going to work out.  

This is the Midwest, so it's ALWAYS white woodwork & ceilings!

However, I am seeing some mold in the shower ceiling and a little under the master bathroom on the first floor.

No tenant wants the crap water from the people upstairs leaking through their ceiling.