You budget your anticipated costs going in.

I anticipate on getting a FHA loan to secure financing. 

I pretty much came to this conclusion after making the thread but now I'm much more confident this is the way to go - I'll suggest they keep the house and take out a home equity line of credit while I act as a the project manager so to speak for a cut.It's good no one will pay capital gains tax, but what kind of tax can I anticipate for either of us in the state of TN (even a rough estimate would be helpful)?

The more years we track our home value, the closer that value will come to it's anticipated value.Therefore if we take our 100k home with a 20% downpayment, in a perfect world it would be worth 103k next year and we would owe roughly 79k on it. 

Who is doing the work & the anticipated quality of finishes is needed to give a rough estimate.

Quick estimates for BRRRR and whether they will cash flow in the future should be based upon the future debt service you anticipate you will have on the property, because that will be a big factor for determining your cash flow.

Your cost to build is likely going to be more than what you're anticipating.

I don't anticipate much more appreciation.

Even if you don't plan to do any of the work yourself, it provides a quick and accessible overview of the issues you can anticipate needing to address.

I recently purchased Quickbooks Pro 2019, and the learning curve is steeper than anticipated!