What to do with the dirty water (whether that be because of food, shower water, or bodily discharge) is the one that worries me the most.

Case workers look at things such as disability, are the potential tenants collecting food stamps, child support, do they have other income, SS, how many children, what ages are the children etc etc etc.....In your earlier comment you said average for 3bedroom is around $900.

We may have three or four different purchases (to keep the personal items separate from the individual business expenses.) 

Some common items to note: roof, electrical and plumbing, window updates.

They are one of the higher maintenance items and seem to only last a few years before being loud, wobbly or needing replacement. 

Look at the property when you buy it to see what the estimated shelf life will be for major items like roof, HVAC, floors, Kitchen, driveway, etc... 

Do you know what the typical items banks consider in giving someone a loan or line of credit for their business are?

If it's a triplex and each unit needs the same work... then you need to multiply times 3 plus any exterior or shared items. 

I have a list of 12 items. 

It's like asking "What type of food is good?"...