Question: assuming an ideal brrrr that has all investment extracted at the refinance, why would you choose a low cost market over a high cost market?

From a tax perspective, I am assuming you would like recognize $0 of the gain on your property in this potential 1031 exchange. 

It's an estimated cash on cash return given current rental rates subtract expenses assuming 7% interest rate, 10% management fee, 5% repairs, 5% capex and other expenses like mortgage, insurance, tax. it's a estimate to tell you what properties to analyze vs ignoreyou can see the are pockets of negative returns as well as pockets of positive return. this is to supplement the data @Devin Conley provided

You wouldn't want to pop a 2% balloon unless you sold the property, but make sure you write it as assumable so you can sell it.  

Depending on comfort and cash, it might be a viable option as you can build equity and then sell without having capital gains, assuming it's your primary residence and you've lived there for 2 years.

I assume the PM side (we use the investment management arm).They have to do their due diligence to make sure you are who you say you are.

I assume your wish to use a HELOC is to avoid paying interest when you are not actively rehabbing a BRRRR.

I assume you’re going to have to target just accredited investors as the judge would make you give anyone else their money back.

Plus, with it being just myself running my own business, and after reading up on how many cash buyers other wholesalers have put in their network to buy properties, that are also sole proprietors, I'm going to assume that having a huge cash buyer list is not really efficient at this point in the game.

With my CFO clients, I generally assume a 35% operating expense margin (which excludes vacancy and mortgage payments) to start with and adjust from there.