If she wanted cash in addition to refinancing the current loan balance you could also look at getting a HELOC on the property if you have sufficient equity to pay her back her portion of the equity owed.

Timing the sell of cap. gain after being converted into a stock.

I have an 8-5 that brings in just under 100k and I work as a part time realtor(sold 3 houses last year and had a rental deal too) and I bartend most Sat nights(300 a night, working 4-11)If I sell the 2 family, after 15% cap gains and 2% to the buyer agent and lawyer fee and pay off all our debt(wife and myself, not mortgages) We would have about 150k left over.If I sell the cabin, after agent fees and cap gains we’ll probably walk with 60k.Would keep pushing forward?

You have 180 days to complete your purchase.I'll reach out via pm with some additional resources including our youtube channel.

Get the owner out and convert the basement back just enough so its not a additional unit. 

I'd recommend that you weigh the potential benefits against the additional workload and potential difficulties that comes along your way.

You have a lower interest rate on the mortgage, but if you turn it into a rental and sell it in 5 years, you will have to pay capital gains tax. 

I am a newer investor (currently 1 short-term rental in addition to my primary residence) looking to purchase a property that I will make into a short-term rental. 

Do they have to pay taxes in the US and do I need to withhold anything from them before paying their interests or will they report their gain in their home country and pay taxes there and nothing in the US?

If you are going to purchase SF homes in lower barrier  C/D neighborhoods be conservative with your debt, set aside plenty of reserves and consider half if not more of your appraised equity to be the result of a generous appraiser because you will likely never see the equity converted to a realized gain.