You’d want to check with Furnished Finders to see what you could get for the property on a “medium-term” basis rather than short-term.

I like the idea of a lender looking at the deal and not pulling my credit (again), but I'm wondering how paying such a lender back would work, considering a (likely) higher interest rate and short amortization period.

The message that the sellers are receiving provides a callback number.

This seller bought it for 7700 and selling it for 40k.

I have a seller finance deal I'm working on and that I love because it will be prime rate or lower. 

DSCR + seller financing would allow you to get to 10% down.Happy to help on this! 

Upon looking for a home to invest in, we noticed the seller only allows us to see the property if an offer is made.

If you'd be in default where seller can sue you for damages above earnest money and real estate agents can sue for commissions, then you may want to consider those potential costs before making your final decision. 

Gathering all the information will be more time-consuming, especially if the seller is an individual rather than a big corporation.2.

In other words, he probably can buy the house.When talking with the seller, you can use the situation to your advantage.