@Nathan Frost- correct -the " interest " only payment  is often made  monthly along with the  monthly taxes and insurance so the only thing missing from this  sort of payment  would be the  principal  amount that  would be  required  on a normal amortizing loan  (  which isnt a huge  amount  ) 

Be sure to advertise exactly what SORT of charging your property offers as there are like a dozen possibilities.Everything past that is speed of charge or dealing with billing infrastructure. 

I have researched the business and I have contacts and connections like family friends who are contractors/ have done some sort of real estate fix and flip.

We like them and want to try and make this work, but wonder what sort of incentive they have to get our rents up higher.

I could charge an additional fee to have access to it, and have them sign some sort of waiver indicating they accept all risk and won't sue me if they hurt themselves.

You will need a real estate attorney who does this sort of work, your CPA needs to be involved and it sounds like a lender.

I haven't done so yet, so I don't know what sort of credit limits I can get.

Sort of.When a lender agrees to a DIL, they will own the property subject to all other loans, liens, possible lawsuits, and taxes due.

I have used hard money as a sort of bridge to longer financing, for example to fix a place up and stabilize it then move to a 30 year fixed product, whether that be conventional or DSCR.I do not think hard money is a good long term option as it is expensive, and STR's are long term investments in my eyes.

Some jurisdictions, like I think Miami, makes the homeowner take an assessment of some sort, but I don't think that's common.