It depends on Johnny's tax rate, and how much employment income he already has. 

Sell - Would prefer to avoid this to keep my low interest rate (3.3%) and avoid fees/taxes. 

Cost segregation studies can offer real estate investors massive tax benefits.

Any ballpark idea what percentage our property taxes would go up if we went from 2 to 3 units and how does that get plugged into the calculation?

I am also extremely interested in Portfolio loans, but I have zero contacts dealing with those types of loans.Finally, I have an 'excellent' credit score, no debt at all besides 5 other rentals at 75/25 LTV (all cash flow positive) and a job that I claim over 100,000 in taxes, and have three years of consistent tax returns showing that.

She might not qualify for another loan, unknown it depends on if she can show it as positive rental income but with your plan it sounds like she won't have tax returns in the future to make this work. 

I learned from my mistakes, stopped overspending, lived within my means, and paid everyone I owed money back.

I also got the taxes reassessed and cut by more than $7k per year, due to the tax assessment being overvalued compared to my purchase price.I just went through the process of getting a 25-year commercial loan put on the property with my usual lender.

(plus higher property taxes due to the new assessed amount)2- I don't have cash for the rehab yet, so any advice on going about sourcing the 100k?

I have done short sales, tax lien purchases, sheriff auctions, wholesaling, / buying from as well as providing, PM about 500 doors growing to 1k in the next 17 months.