I guess it is up to the lender's risk appetite 

I am nervous about things like not being up to code or having to install fire suppressant systems...

But it will depend on you: your risk appetite, access to capital, goals (metrics!)

The contractor commented that while the elevators and sprinklers are grandfathered in, if I had to extend them in any way the grandfathering would be lost and I would have to replace them all with new code-compliant systems.If you got a new tenant that was perfect but required additional fire suppression, would you want to replace the whole system for them or would you let the space go vacant?

What is my risk appetite?

My appetite for learning and understanding investing and real estate has been whet since that time.

I've finally matured, as one can with respect to financial matters, given that all humans have appetites, some for better and others, for worse!

There are "poor" landlords and slumlords in all sizes of properties.That said, in our experience, there is the no-mans-land of small multi-unit properties (5 - 20 units, say) where financing will be commercial and, if not a converted house, the property will have the commercial systems one expects to find in larger buildings (fire alarm and suppression, security doors, common boiler, common laundry, etc).  

@Nick SabatWe still have to manually test smoke detectors twice a year (insurance purposes), but in bigger buildings are experimenting with being able to tie into the alarm and suppression system to get alerts and check status.We may have a deep retrofit renovation ahead of us this summer (depends how things go at auction in a couple of weeks and our velocity with all the other projects) where I plan to install a "smart" panel which will allow us to remotely monitor and control individual circuits.

Each city has their own unique characteristics and advantages/disadvantages so it comes down to your appetite for return versus risk (as well as your timing of holding and budget).To answer your question around financing, it depends on the amount of budget you are willing to work with.