I have enough funds to cover vacancy, so I am not too worried.As far as it being in the hood... 

Find a buy and hold property with plenty of cash flow to cover your property manager.

If monthly for a 2 bed is $2,000 and you are able to ask $250+/night you would only need about 30% occupancy (roughly 10 nights/month) to cover costs.

The question is, how will your property be financially situated, absent STR income, if you switch to LTR, can it cover the debt?

Do underwriting guidelines allow for one conventional mortgage that would cover the two duplexes or three houses respectively? 

San Antonio covers a big area.

The problem is, the HELOC will not be enough to cover the cost of the property.

I would recommend keeping a minimum of 15% to cover CapEx and Maintenance reserves.  

Making sure I have all the right documentation.I've been out of real estate for about 10 years, and probably didn't do this part right in the first place, so trying to cover my @$$.

@David OlsonI am in no way an expert at this but I believe when you are making a cash purchase the main team players are:Attorneys, Title Company, Inspector and Appraiser (occasionally)Attorneys: Using legalese to get the purchase contract in writing Title Company: Perform due diligence to make sure there are no liens against the propertyInspector: You already covered thatAppraiser: To determine the price of the property at its current state and after repair value.