If you just take the 13,835 financed at 6% you are adding 83 dollars a month. so a double whammy.Now, lets consider if rates drop to 5.5% in 24 months (not a prediction just a what if) and you could have refinanced at a much lower costs then the above scenario in what you paid in pre-paid and additional interest. on the other hand, if rates for your same scenario after your 5 year payback period is 9, then you will have an asset with a much lower then current market rent.  

However, you have the additional question about if and how you might enforce a judgement in another country. 

If they have a loan at a favorable rate, I give them additional money to take over the loan.

So your additional ~240 SF could be the foyer, hallway and bathroom spaces that are allocated by percentage to the unit.

This money will be used to pay down some debt I have and also purchase 1-2 additional rental properties.  

Given that you're not married, that adds some additional complexity.  

(replacing the original HELOC debt) However whether the interest for the  additional $200kish of loan  will be deductible will depend on 2 things: -How were the renovations paid for?

If you need any additional help I will tag @Crawford Peay who is an experienced  property manager perhaps he can help. 

It sounds like you’ve got a solid foundation with your rental property, and I love the ambition behind your plans to build a property management and maintenance company—it’s a great way to take control of your investments while creating additional opportunities.Best of luck to you! 

There is no additional valuation for the STR business.In the end, past performance is not an indicator of future success.