You don't need an inspection to know the age of a roof.

I'm the mindset that it's better to own fewer high quality properties than lots of inexpensive ones (e.g. all those roofs, HVAC etc to replace in the future). 

Why would you give them free rent with they still have full access and use to the stove, refrigerator, walls, closets, flooring, roof, garage, lawn, etc.?

If the roof’s age is unclear, it might need replacing soon.Electrical systems can be tricky in older properties.

Many carriers have ceased offering new policies or will only accept properties in very nice condition with verifiable updates to the roof, electric, hvac, and plumbing.

I would say look at the big ticket items, roof, foundation, electric, plumbing, HVAC and assess from there if anything needs to be done 

He eventually put a new roof on my building and did an excellent job! 

Most recently, I worked with a client out here in Colorado that let their parade of homes house (from 25 years ago) in a gated community literally fall to pieces; mold between window panes, water infiltrating the kitchen due to lack of roof repair, patio pavers crumbling apart, downspout misplacements that caused water infiltration into the living room....just a mess. 

As Jay mentioned, massive power requirement that will not get cheaper in time, and along with large water requirements for cooling the rack systems, so targeting locations that provides these necessities is key.

Charming Little 3/1 - We are remodeling all inside and out including new roofing, this is our first project out of state, it will be a BRRRR, hopefully first of many to come.