As a landlord, I'm more put off by your short term lease than the dogs (we allow them, excluding bully breeds).

I am hoping to be investing and living in Portugal shortly. 

banks have to hedge to ensure they dont lose money when rates go up. hence they charge for rare extensionon new constructions its preferred not to lock rate until its ready for possession. if you dont need to pay for rate lock extension if you walk away, suggest you go with new bank. 2 weeks is too short for a large bank to get ur loan ready to close.

I think she would take a partial cash offer, if we could pay off the rest in a short amount of time.  

Short-term rentals might fall under Loudoun's new laws about AirBNB-type rentals, which at this time require only registration (taxation and permits likely to come in the future).

Tim, I can provide you a contact that I've used to look at short-term rentals in Miami.

I'm in a career field where I am likely to have multiple NCR assignments, and have many friends and colleagues there, so I should have some advantages finding quality tenants (possibly myself if I catch another assignment in the area).Budget: I'd prefer to keep it to a no down payment VA loan, which caps me around $680K, but I could put some additional down if i find a particularly good deal.Area: I'm targeting a SFM home  or townhouse in Arlington, Alexandria, or Falls Church (short commute to Pentagon and FT Belvoir), which I can rent easily to upper end military families or local professionals.

As you acquire more you may need to up the number but in short, no there is no true formula. 

If you are happy with an annual lease, that should be a pretty safe bet in most places, but if you're talking about short-term rentals, make sure you're somewhere between Kissimmee and Davenport in a neighborhood that permits it.

If you have any equity anywhere you should easily be able to find a short term loan for $5-10k.