I've seen some lenders offer as low as 15% down on an investment property but the terms they'll impose for doing so aren't usually worth it imo. 

., short-term rental, mid-term rental)?

Long term interest rates should continue to increase.  

So if you are looking to hold long term, you must take that into consideration.

These are top drive-to destinations for much of the Southeast, so short-term rentals here can generate solid cash flow, especially during peak seasons.The area is also seeing steady growth, with more infrastructure and amenities being added to support visitors and new residents.

Sometimes the long term capital gains are palatable and it may make sense for you to pay the tax rather than force a bad deal.

Has anybody found a workaround for this or would the seller simply have to hold the note long-term without the option of selling it?

Placed another 8 unit portfolio under contract in early March, unfortunately contract expired on April 23rd, couldn't secure favorable loan terms that wouldn't allow portfolio to meet cash flow numbers because banks changed lending practices due to Coronavirus pandemic.

My ultimate goal would be to buy fixer-uppers to turn into long-term rentals.

Since you’re considering converting the upper unit into a short-term rental, you may also want to implement strict rules around smoking or strong odors in your house rules to avoid future issues.