It’s a very broad question that encompasses dimensions of risk and risk-adjusted returns. 

Would love to get this all straight so I can start adjusting my strategy confidently!

However, since you already filed 2021 and 2022, the adjustment will be happening on your 2023 taxes.

If your plan is to sell/refi before the loan hits it's adjustment period, this seems like a no brainer (assuming there are no pre payment penalties). 

HELOC is an interest only payment, an adjustable rate, and you can draw funds up and down from $0 to your total line amount.

I think >50% chance US will be in mild recession in 6-10 months, as Germany/UK/Canada/New Zealand/Ireland/Finland already in recession due to they have 3-5 yr variable/adjustable mortgages and corporates also do short term debt, so their central bank Hikes hit them faster than US.

Is it an adjustable rate?

If you can swing it, I would tell her that you are going to have to adjust the rents to the market level, and give her as much time as you are reasonably able, maybe 3 to 6 months to vacate, provided she's paying.

The cost basis rarely stays the same over time, and once it’s changed, it becomes the adjusted basis.

Identifying a d purchasing properties that are undervalued due to under market rents caused by owners with a lower purchase basis that are terrified of losing tenants and raising rents, will definitely provide you with immediate upside appreciation when adjusting rents to market rates as well as covering all your holding costs and a cash flow reward every month.