Most likely a "discount listing" Owner pays realtor a small amount upfront to add it to the MLS.

At my brokerage they specialize in STR management.

Also , I would love to connect with any agents who specialize in STR market in Boston Mass area. airdna is pretty accurate . lenders use it to assess rental comps for short terms rentals when financing a short term rental  I use it for DSCR loans as well; it is accurate yet conservative because it gives you the median 50 percentile for the area based on comps.

Some lenders offer discounts to return borrowers so maybe look into both flip and DSCR rates when finding a lender. 

You can find one that specializes in STRs. 

- The market is in a little bit of a lull right now (buyers market), its a great time to buy, but slower time to sell (my primary business is flipping houses) I can supplement my flipping business by providing project management services/consulting, helping investors find discounted properties, etc. etc.

Despite if it works and or what anyone says... arbitrage will always  have a special place in my heart since it was what got me started in this RE game. 

Regarding finding discounted deals......That is the reason why I started a wholesaling business. 

I specialize in kitchens and bathroom remodeling, and have a custom cabinet shop.

So keep that in mind when using a special lock system.