You can pay for a PMC system like Buildium, Doorloop, Hemlane, etc., or try to piece together several free systems.

With a large group of say 16+ guests a $2000 or $5000 weekend is much less expensive when multiple parties are paying.   

You can find a VA or a younger person to pay.

I would rather pay a little more now to build a foundational system for growth. 

That should allow you to avoid the "pay and stay" rule.

Should we be doing this HELOC if we are unable to pay it back in full at a later date. 

(On that type of deal it should but play it safe)Even if the seller can show you a current policy and that is what they are paying now you as the new owner may not be able to secure that same rate even from the same insurance carrier.

I actually did get someone, but then they tried to hustle us with a wayyy lower price when he went to pay

I ended up paying about 1/2 that with another service.  

Let them live in it and pay me a rent for a while, And then, offer to sell it back to them in 5 years at $1,000,000.