Here's how I would calculate Capex: total up all the big-ticket items that haven't been recently addressed (roof, plumbing, electrical, HVAC systems, sewer line, kitchens and baths/in-unit upgrades/appliances, parking area/driveway, landscaping/exterior, etc.).

Foundation and plumbing is already cost 12k.

Depending on the  need of any mechanical updates(electrical, plumbing, HVAC, furnace, etc), you might be able to get away for less than 20k.  

Some Inspectors will sign off on site, and others will make you remove enough drywall to check framing, electric, and plumbing.

The older you get the more you have to pay attention to: mechanical systems (electrical, plumbing, HVAC); roof; foundation; windows; rot/insect/termite damage; insulation.

The property is already cleaned out and is only foundation, framing, and some old plumbing and electrical.

The ad is for just one single house, not a list of 23.My current ad does not mention Hugh Hefner, indoor plumbing, outdoor cats or the problems people have with staying in a motel.

For some people that's like a handyman or DIY doing electrical and plumbing, vs a licensed master electrician or plumber doing the work.   

I have a CBC six-plex in South Carolina that needs complete rehab.Two identical buildings 2600 sq ft each. needs roofs ripped off, new trusses compete re-roof, new wiring, new plumbing, new HVAC, new kitchens, new baths.

@Alfred LittonA couple tips I can give you is to ask your insurance company if they give utility discounts for things like new roofs, HVAC systems or redoing plumbing, electrical etc.