I got very lucky in that we have great people running the place, but I've spent a lot of time getting other options ready because I know it could change instantly.  

I get instant updates when there are new listings in my market or on any properties I follow.Redfin rocks!

Most of my tenants won't be able to instantly replace a major appliance or water heater if it goes out.  

I do this so often that I created an online tool which enables me to instantly estimate a break-even price (where rent equals recurring expenses).

Instant turnoff.

That was my main reasoning with putting money down -- I would have instant equity in the house that would keep me from getting in under water.

@Spencer Keables, some investors are more motivated by instant big profit rather than long term cash flow. 

Buy with instant equity so I have options.3) Have many options to do with my time and funds.

Eric,To answer your question, I think you are looking at the worse case scenario of not being able to fill the unit(s) in a timely manner so that your tenants are paying the expenses including the note.I look at the analysis I do and factor in the worse case, although you may find units that are filled and would instantly supply current rent that goes toward the expenses.Because you have a W2, as I also do, if you are not able to pay the expenses "until" you get it filled "if" it were not filled then you need to think about that circumstance.

instant curb appeal and makes a great selling feature to potential tenants.