After a thorough review of systems, we had plumbers troubleshoot and repair/replace a couple of small chronic bathroom leak issues, and electricians installed a number of end-runs back to the panels so that rooms could each have window A/Cs running without tripping circuits and other such issue.

Hey @Devin Bost, I would highly recommend a few things to help with this. 1) Have systems and processes lined out for any emergency you can think of.2) A spreadsheet of subcontractors/ vendors that could handle the situation that arises (plumbing leak, electric out somewhere, etc.)3) Your cleaning team and handy person should be utilized for some things.4) Something like Breezeway can give you 24/7 support around your property with a dedicated phone number line.

I had a client buy an REO property and there was a water leak.

The first sign that a roof is failing is when it leaks.

HVAC, Plumbing, Sewer, Roof leaks, etc. 

I am debating whether i should just fix the shower pan. or, rebuild shower as well just in case water leak is coming from shower walls. what do you think? 

They know the tenant base, median rents of different areas, how much to increase rent each year, ranges of repair costs (ex: tenant calls and says AC isn't working, no hot water, faucet is leaking, the HVAC system goes out).

Do not believe the lie that you can adequately manage your vacation rental with your iPhone and some far east "customer service agents" to take the occasional phone call.

In these instances, you'd have to check things like flooring, plumbing for leaks, roof for leaks, hot water heater, and heating and air conditioning units. 

The roof is fine until it leaks, decks are fine until they are not, things wear out, line blockages don't happen overnight they most often are buildups over time until the result IS seen overnight.