Question: I'm an agent trying to deal with an owner on a small commercial prop says once a buyer signs LOI they can get any relevant leases do their due diligence as well as do their inspection before going to contract.

These tenants ahve all of the signs of never paying you or paying a little as their balance continues to rise.

My market is similar to what you are describing and I too see signs of a suckers rally and reminds me of 2004-2006.

Is there a way I can "co-sign" with one of my parent's credit cards and be on their credit history in order to boost my credit score? 

However, I cannot be signed into both her account and my own VRBO for my 2 properties at the same time.

What has been the conversion of those leads to signed opportunities?

Quote from @Tod DuBois: Another Furnished Finder POT cancelled on me after I went out of my way and paid to review them on Key Check and signed up for Key Check contracts, made two contracts, allowed a pet and still, two days before the check-in, they did not sign.

These things never seem to work out well 10 years later when you need them to sign stuff. 

It was easy to sign up with Square.  

Also no credit reporting, so I signed up for Landlord Credit Bureau at my expense.Hope this helps, for now I’ll be staying with Hemlane.