Is there a way to create an interest list where you could get people to sign up if they are interested in renting in a particular area? 

The snippet you provided is a bit ambiguous which may itself make it unenforceable.I think your goal should be to get a signed doc from the parties to the agreement saying an STR is permitted under the agreement.

Some may have you sign something that say you don't intend to live there ever.  

For anyone considering signing with them, do some serious research first.

I have a rockstar attorney who does Virginia, dc and Maryland.

I went to his preview event today,  where they give you some basic info, and try to get you to sign up for there 3 day course for $997.

Do you have a disclosure or buyer agreement signed with this buyer?

You can pay a flat fee listing service a few hundred bucks to upload a listing (you'll have to answer calls, schedule showings, set up a lockbox, get a sign, vet potential buyers, avoid scammers and people trying to sell you stuff, negotiate and manage the sale yourself).

A certified letter is good because they sign for it, acknowledging receipt, any other forms of written communication you can get to document that they were notified of the hazard probably also helps. 

Its a tough subject because logically, they are joint and several guarantys so rationally a 100% guaranty from each of two people (one 740 one 680 for example) is ALWAYS going to be better than just one 100% guaranty from someone at 740 (so it wouldn't make sense to have a better rate for the latter)The problem is that there is fraud and "straw borrowers" out there where someone who is not involved in the property signs on to boost score and terms - so many DSCR Lenders in response either do the "non-rational" thing and price to the lower to avoid the fraud or use the higher of the two (and either be a little loose with things or just stay vigilant on any funny business)