.- If you build a good/great portfolio, you will have multiple exit options you can evaluate annually or whenever.3) Don't overleverage beyond your risk tolerence.

As noted, commission are always negotiable as are brokerage options (full service to discount companies that pretty much just post it on the MLS and you work with all calls, offers, etc) and an agent can go over likely net out scenarios with you and give you an idea what you likely will be able to net after closing expenses and paying off the mortgage balance. 

i agree that a new purchase at 75% equity will typically not have significant cash flow and may even be negative when properly allocating for all expenses.Investing to max equity without reserves is risky and you indicate would result in stress.  

However, currently there are no options for a foreigner to get a cash out refi on their property in Costa Rica other than for construction on the property itself.

I think a mix might be a good option.

Typically, this results in the loss of hundreds of affordable housing units.

After a quick search it seems like Baselane is a good option, does anyone have experience with it?

I'd like to move forward with option "b".

Viator could also be a good option to explore.

Typically, we see anywhere from $600 to over $1000 per unit (maintenance and turn costs)  depending on these factors.