As for cash or not I think it depends on rates, your level of risk tolerance, and what the opportunity costs is for that money. 

It’s a solid option if you’re confident about refinancing before the higher rate kicks in or if you want to save more month-to-month early on.Option 2 (3.5% DP, Permanent Buydown): Lower upfront costs free up cash to invest elsewhere, and the 5.4% permanent rate adds predictability.

I am pulling in between $500 to $1,000 from mine each month even at a high interest rate with about 25% down for each. 

The agent will have access to the biggest platform to get the property sold though, the MLS, so forgoing even a cut rate agent will create more of a loss than the agent fees themselves. 

It’s a sales pitch for you to invest with them at extremely lucrative rates for them.

I'm trying to decide the smart investment decision - continue renting it out at a lower rental rate OR selling it and trying to find a potentially better performing asset to re-invest those funds in.  

Quote from @Sam Epperson: let's say I come to an agreement with the seller for them to finance some of the deal. let's also pretend the seller owns it with no debt, and we agree to 5% down, 5% rate, and 10 year balloon. how are we drafting this legal document?

This isn't so much due to interest rates - these neighborhoods have been this way for at least 4 years.

I've seen where people add so many loan extensions with optional payment.Say 1k gives you a 1 or 2 year extension and this can be done 4 or so times.This agreement could be changed so many ways to make it work.You could offer a higher interest rate after 7 years to extend to 15 years.

For a purchase or rate/term refinance, that would be 70% LTV; for a cash-out refinance, that will be 65% LTV.