I don't know your living situation but if your paying x,xxx for rent or a mortgage and instead by living in one side and renting out the other you will be paying y,yyy instead and y is less then x that's great, especially if you can rent out your primary residence and make income there too. 

Here you can get a little cashflow + appreciation + mortgage paydown while other areas are just the former two. 

Your question on the loan - do you mean total mortgage (interest and principal) or just principal when you say 'paying off'?

With some proper planning and the funds to lock in materials early, you can have an efficient build, but certainly not fast.

My goal is to live in the home during the winters, maybe 3-4 additional weeks for vacation, then rent it out to help cover the mortgage the rest of the year.  

There's obviously opportunity here to build this out and turn it into a basement apartment, which I think would cash flow because of course there's no mortgage. 

It's an estimated cash on cash return given current rental rates subtract expenses assuming 7% interest rate, 10% management fee, 5% repairs, 5% capex and other expenses like mortgage, insurance, tax. it's a estimate to tell you what properties to analyze vs ignoreyou can see the are pockets of negative returns as well as pockets of positive return. this is to supplement the data @Devin Conley provided

Hi Aubrey,International lenders don't exist for real estate in that no lender in one country will give you a mortgage loan in another country.A good service to estimate revenue in Costa Rica or everywhere in the world for that matter is Aidna.

They wouldn't be able to get a mortgage, but would have to do some kind of SBA loan or other commercial loan for the business with the properties as part of the business.

I am looking for a mortgage broker sponsor.