Even if you can manage that, I think there are minimum resale time frames, so you would have to be able to hold the property the required length of time, all the while paying holding costs.

Maryland real estate law can be surprisingly complicated compared to other states, which can be seen in the length of contracts us agents use.  

Go a little lighter on the credit requirements and tighter on length of employments and references to find your best long term renters here.    

Obviously nobody hopes that they have to go months without finding a tenant, I was just concerned with whether or not I should worry about being able to sustain 100% vacancy for any real length of time.

Required documentation is dependent upon the length of time the borrower has owned the property.Rental Income – Subject Property For FHA MortgageLimited or No History of Rental Income Defined as when the borrower is purchasing or does not have a history of rental income from the subject property since the previous tax year.

Loans for investment properties are not eligible if the transaction includes non-arm’s length and/or at-interest characteristics5.

I don't see any real downside to re-financing at this point as long as the tenants are paying for the increased length and interest of the new loan. 

Business transactions must be at arms' length.  

Length of stay may vary from city to city and some are declaring anything less than a full month as STR.So if today there is no such restriction(s) and it is a viable business model for you now, how long can you assume that will continue and if it changes, can you survive the change.CAVEAT EMPTOR.

To design a deal you need the type of property, a price, equity amount, management intent, what are customary sales in that jurisdiction, insurance matters, length of purchase term, exit strategies, what rights might be conveyed, how maintenance and repairs will be handled and how payments are to be designed that are appropriate and how the are applied.