I'll put them in order of what I prefer and why:1) Save up the cash using cashflow from my current portfolio and W2 income. 

This property gives me significant income, so losing it would be an extreme loss.

If you don't have enough to invest locally can you increase your income and savings to be able to invest in 6 months or a year? 

The best way to connect and learn is to be in rooms where it's going down.In terms of captial your best bet is to focus on a primary income that cash flow sufficiently, saving as much as you can and doing something real estate related so you can get familiar with the industry.

Six figure income is still impressive for any residential SFR..optimally rates improve and so will rates of return with a refinance.

If you have some capital, income, and decent credit, buy a 4-5 bedroom house and rent bedrooms. 

Is her goal to be nice and provide some of the gains or reduce her taxes by trying to split income between her and her ex?

If the way to increase the selling value of a MFH is to increase NOI by increasing income or decreasing expenses; why are the majority of sellers putting their properties on the market with under market rent?  

It's usually someone with a high W2 income buying a primary then doing Mid-Term or Short-Term Rentals with an ADU. 

Im a huge fan of themI think both - they will bridge the gap with middle-income renters and also appeal to the higher-income bracket.