I understand tenants concerns and want to figure out a win/win situation here.I was considering buying 1 A/C window unit or indoor door A/C unit for each property as a backup for emergencies.  

I have two backup offers at the same price.I don't like to have very many one-bedroom units.

Back up.

It does back up to a major, heavily trafficked road, but has an 8foot security fence, and road noise is somewhat dampened by a corner store behind the house.

If you have multiple offers, you can also put one of the others in a back-up position (if the buyer agrees) just in case the first offer doesn't work out.

I've had a similar issue with a back up with a dishwasher filling up the sink and it was a slow drain that need to be cleaned out to solve the problem.

I'd encourage your agent to keep holding open houses and trying to solicit a back up offer.

(we have tools, equipment & experience + a back-up crew of help, if repairs end up being something like major electrical/plumbing issues.)BUT, even understanding all of this, as best they can at this point, they still seem to be oddly/overly concerned about "what friends will think" and how to handle the leases and paperwork "without roommates finding out".  

A bonus question, I have other rental properties with large equity in them, can I apply HELOC now (for backup) while applying the TIC loan (suppose to close escrow in 30 days from now)?

Family first places your investment plans on a back burner.