What you are asking is the same question that everyone has when you start in real estate investment.The solution for financing is what Jay mentioned.I think you need a real estate agent that can help you here.

And then the solution was to block my unit off as owner-booked, or to “resign the listing.”

This can be a more cost-effective solution than having separate water heaters for each apartment.

Yes, there is a solution, but it isn't a quick post.

Try to find a solution any future issues like this.. 

It is not a solution for long term.

Put down glue boards, where the mice were first noticed. and several other places. ask tenant to monitor and leave extra glue boards for them to replace if mice is caught..

Thanks I would look to AirDNA for this - they have long had pretty good (guidance, not perfect) rentalizer solutions for projecting revenue, but have recently added good info on expected expenses and the property managers in the area (for at the very least coming up with expected operating / management costs) etc

thank you for great suggestions, Jonathan.are there any web solutions or systems out there to collect rental payments?

I immediately looked at the portfolio and raised some rents I had been putting off doing which was a start in a better direction but not an actual solution.