Our original budget was $14,000, including closing costs, but replacing 2 ac units and 2 high efficiency water heaters put us over $22k.Did you work with any real estate professionals (agents, lenders, etc.) that you'd recommend to others?

What's the most efficient way to do them? 

My experience has been that BRRRR works best/most efficiently if you are going in all cash on the front end, waiting for the seasoning and then refinancing.

I have seen and heard of many bigger companies acquiring these houses very fast and efficiently and I was wondering if anybody knew what they do so I can learn as much as possible.

If you are buying them off the MLS...then a lot of banks can do that reasonably efficiently.  

We plan on replacing all of the windows for energy efficiency.

Connect with other landlords and see what systems and processes are they using in their business to allow them to manage the property efficiently

Cons - lesser quality control, more prone to mistakes, fewer efficiency, inability to scale.

Shafi, unfortunately, the SFR experience doesn't always efficiently transfer to MF experience. 

Most of our value will be through operational efficiencies.