This could be less costly and smaller hurdles than you would have with hard money lenders.

Also, what are some other low cost amenities that I can add to my STR that will yield a higher ROI?

That's like asking how much it costs to buy a car. 

Americans are seeing rising debt as it is.

My 2 cents is prices are crazy inflated right now, but believe it or not I think it will continue because of continued demand pressure for the area from people fleeing higher cost of living areas and moving there, with access to 87/17.

How much upfront costs are typically involved in a project before you know if it's a viable project to pursue? 

I've done a rent credit for the price it would have cost to me to have the property cleaned in a past rental due to immediate turn around.

I'm sure OK has its share of dumps but you really have to drive around FL to truly appreciate how much low-cost housing there is.  

You cannot deduct your rehab costs until the property is in service. 

This could easily cost you $10’s of thousands if you plan to stay in the home 5+ years when you return.