My cost wont necessarily be the same or comparable as I GC my own projects and have trade skills.

To Sum it up, its a good idea if you can exceed the cost of capital (higher rate than your cost of debt) with what you earn on your heloc/debt you pull out and invest.The question is how much gains above is enough to substantiate the risk of your variable interest rate, well thats up to your personal investing criteria.

To simplify the scenario I'm envisioning let me put it this way: what does a BRRRR look like when one of the parties contributing to the down payment and rehab costs ultimately ends up being the renter as well?

Account for all costs, including closing fees, holding costs, and repairs.

Closing CostsMake sure you also budget for closing costs, which are a collection of fees and payments made to the various parties involved in your transaction.

Selling and buying something else you want keep and doing a cost seg in would help with the tax burden probably better in this situation.

While the borrowing costs are higher, I’m exploring strategies where the returns could offset this.

Kudos to you for doing something to create a secondary income stream. there are 5 income streams in RE rentals, possibly six if you do things a certain way.The reality here is your model (buy box) is suffering from too high an entry and too high a cost of capital.

Additionally, the cost to create a business here is not as inexpensive as the United States, in some cases it can cost thousands of dollars to setup. 

Hire an attorney to handle this, or it'll cost more and take longer than necessary.