Once you have a working knowledge of these items then you can move forward.I would caution however, apartment building take a lot of funds and more than a little cash to get into. 

As mentioned, review the Lease. it should be explicit for a common item like the door.

This will boost your preliminary knowledge base exponentially, and thereafter your confidence in offering on properties.Once you have a bit more comfort with the straight forward items (or while you’re learning about them), get a property under contract with an inspection contingency of 14+ business days.

The HUD approved FHA 203k Consultant determines the price as well as the items required to be completed to meet FHA MPR/MPS.

@Eli M. hate to say but all of your items you just mentioned increases your value at minimum.

She claims she left everything exactly as she found it -but has admitted to the drywall holes and replacing the doorknob, which leads me to believe she's not being forthright with the other items.

Depending on its age, cracks in the brick may be  a normal occurence or a serious problem (if the house is newer & you have cracks in the brick, this is an issue)The foundation: again, the level of concern on this item depends on the age of the house..

Now unless you have more than a few deals under your belt, you're not going to know every cost for every item. 

The tenant is now asking if a friend of theirs can have the keys to start moving their (the tenants) items in. 

The knob and tube becomes dangerous when high amperage items are used so if those items kick a breaker then there is some built in failsafe there.