We can't wait to see these set up.

Reducing rent sets a precedent and can attract price-sensitive tenants rather than those prioritizing quality.Negotiating renewal terms can make sense if tied to benefits like lease length or tenant stability, but always ensure it aligns with your long-term goals.

I offer an online payment portal to submit rent payments via ACH or CC - they "couldn't figure out how to use it" so I set us up to accept Zelle payments.

Does anyone have experience of setting up a STR while in the same position? 

Freddie accepts this.Couple of options from here: If you did not set up notes receivable, recognize that you may owe it to your seller and take the hit on a higher rate refi to help him.

My goal is to be filthy rich and set my family up for generations. maybe I should pay the mortgages faster?

Quote from @Marc Shin: Hello,For the financing of a BRRRR, are there lenders that are willing to include the costs of Airbnb set up (i.e. furnishings) in the initial hard money loan for a BRRR? 

Best approach is to have your "team" set, before going out to secure properties. 

Before making that move, consider other funding options like HELOCs, cash-out refis, or partnering with an investor to keep your retirement funds growing tax-free.If you're set on using retirement funds, explore self-directed IRAs, which allow real estate investments without triggering penalties.

@Zach Denny  Similar to what Minna posted above, I have done with a local portfolio lender bank where they set their own lending rules.