And you have depreciation recapture (currently 25%) and long term capital gains.    

I have considered partnerships with a Washington friend who could hold the loan and live there for a year and in return receive partial ownership in the property. 

Hey David, For your lake house, implementing a 7-day minimum could work well, especially if you aim to take advantage of the short-term rental tax benefits, such as the "short-term rental loophole."

I find newer investors over-using acronyms when they don't even know they mean - ROI, COC, BRRRR, etc.The most glaring old school vs. new school knowledge term that I think people should look to hear, not say, is holding paper.

I met with a seller, and we have verbally come to an agreement on purchase price, interest rate, down payment, term length and monthly payment.

Short term loan (3 months) for home and rehab = $203K.

The folks I want to coach me have done over 1100 flips, have many long-term houses, also do wholesaling and short-term.

Have you already closed your first buy-and-hold deal?

The loan is often amortized over a set number of years, but the specific terms (e.g., interest-only payments, balloon payments, etc.) depend on your agreement

Sure there are people who have done it but like Joe mentioned above is why your rate on HELOC is probably higher than your first mortgage so you'd only do it if your balance is really low and near the end of your term anyway so you're just getting it paid off quicker (like the last 1-3 years of payments left) becaues you want to get ride of the monthly payment and improve your cashflow now versus later.