There is a matrix I like from Jeffery Norton that uses the ppsf method and I think that is a good place to start as he has the numbers updated for 2021....however, for my own comfort I want a few GCs to go boots on ground after I have locked in a property through a contingent offer.   

Nevertheless, there is a method to obtaining your answer, and it involves many of the things Christopher mentioned.A bit longer answer is, it requires experience to assemble a team to help determine those costs. 

My focus is to start small and scale with the BRRRR method executed perfectly.

As long as you have a day job, and do R/E on the side, the if your income exceeds $100K, your allowable loss slowly reduces and by the time you hit $150K, the current year loss is zero.

He utilized the BRRR method/fix and flip method, without him I would've never thought of real estate as an investment.Good Luck!!! 

Energy Efficient Home Deductions (45L) – Your property may be eligible for this deduction if the property uses energy efficient assets such as windows, roofing, high R value insulation, doors or HVAC and the property is 2 stories or less and considered a residential property or apartment.3.

Let's call it the "income avalanche" method.

I'm not sure how others do it, but I think this is the method I will try. 

Does the BRRR method work for primary residents or for only rentals, is this a smart idea to use a hardmoney lender to get the property?

@Remberto Teos The goal of the BRRRR method is to pull out most of your capital at the end so that you can recycle it.