You asked about buying older properties and the biggest issues I have found is that roofs need to be replaced, HVAC needs servicing/replaced, and sometimes there are foundational issues (not super common). 

a property that was attached but the next door property had a door to the roof of it with a deck. 

And in some cases, a roof inspection when the HI is not confident or the roof is a specialty roof (metal or tile) 

It was an office building owned by a somewhat shaky business, but did have numerous long term roof leases for wireless providers.  

Basements (if they have them), roof, attic, crawlspace, exterior, and all mechanicals are where all the unseen costs are not in the kitchen, bathroom, etc.

Capex is usually lower, around 2-5%, since major replacements like roofs or HVAC systems are far off.

If a major expense comes about (i.e. roofing repair, hvac, etc) we would split that as well. 

In my case it's probably going to be the roof. 

Until you spend 20k on paint and some new kitchen appliances, but the roof and foundation are still shot and the 100k ARV is more like 70k in reality.

Every 15 yrs HVAC, every 20 roof/kitchen/bath, every 5 flooring...