We turned 9 units, 8 of them probably cost a total of 1000 bucks ,all covered by security.

@Roberto Costa Great, we are so happy to hear you are enjoying the service!

The mortgage on your own home is a "cost"...a one way ticket.  

These corrode over time and, when they break, they cost a lot to fix.  

I have estimated that it might cost as much as $4k-$5k in closing costs so I wonder if it is even worth it?

It's going to be a bit more desirable, since people typically like having fewer neighbors attached to them, and while you benefit from that higher value as an owner, you'll be having to deal with that higher cost as a buyer first.

These houses cost a little more, but I don't spend near what you are talking about for maintenance. 

I have listening to Don Costa's podcast on sales/marketing techniques to get the pipeline loaded full of leads wanting to do with you.I am curious for those who do Massive marketing if there has been an inflection point where there are diminishing returns for the volume of mail put out.

Also whats properties like in Costa Rica?

If you are going to do this, you need to do it from the start, because it will cost a lot of time and expense with the bank to do it later.