You might want to think about pulling up the carpet and taking a look. (2) Maybe the water delivery piping under the floor, hot or cold, has developed a pinhole leak and is spraying onto the subfloor from below. 

Furthermore, what has been your results as far as Delivery %, Response %.

We use ours enough that they will waive their delivery fee once per tenant stay.

I know you don't want them using the box, but there's really no harm to you and it's only until a new tenant is placed, then USPS will change the locks.However, you could let the post office know the unit is vacant and ask them to stop delivery to that address until a new tenant is placed.

Notice may be given by: (A) regular mail; (B) certified mail, return receipt requested; (C) personal delivery to any resident; (D) personal delivery at the property to any occupant over 16 years old; (E) electronic mail delivery to the email address used by the Tenant to submit the lease application.

If they sent you a registered mail change of address they will have a USPS receipt of the delivery.

I wouldn't buy existing. newark is the #1 zip code for new home deliveries under 400k this year in 2023 and is mostly being driven by DR Horton. year of year property appreciation is insane as well more than 10% on the median and average last time I checked the housing stats. if you want to build please reach out. we don't do any brokerage with existing inventory 

Again, plenty of bad agents out there over charging and under delivery, I say good riddance to them.

Are there gas delivery contracts in place that you're going to inherit? 

In the age of same day delivery and on-demand streaming, filling out a form gives newer folks a hit of dopamine and makes them feel like they are doing something positive in their lives.