You will want to consider the transaction fees, annual fees, speed of processing, customer service and knowledge. 

I know someone who does 50-60 annually and they do everything the same in all units/houses.

And if there’s $75K worth of rehab the owners annual expenses are likely artificially low, which is likely what created the $75K need in the first place.

But, that will only affect your ROI, not your annual cash flow.

The loan constant is the annual debt service divided by the loan balance.

First of all you don't have as much control of your expenses, and HOA's love to under-collect annually and then sock you with large one-time special assessments to do repairs.  

Do you guys rely on Realtor.com to estimate annual prop. tax based on purchase price? 

I am going to be flipping about 3-4 houses annually and looking to acquire 1 rental property annually as well.

If your rent is less than what it costs to pay a person to clean then it makes sense to block a day after they check out to allow yourself time to clean.I increased my annual revenue by paying a cleaning person and having same day check-in check outs.

That being said, I have helped a 911 dispatcher, bank manager, medical device salesperson, car salesperson, state trooper, and a mailman to name a few build their dual career to more than $4 million+ in closed annual volume.