Wife and daughter don't like them as they make it hard to clean their hair of shampoo.

Is there anyway their hairs, sons/daughters, 20 y/o “husband” can become protected tenants upon their passing?  

Sometimes you can tell because of rust staining and buildup on the outside of such affected pipes,   but even without that they can be weakened considerably from their original state.On the drain side galvanized branch drains  (1.25 through 2" galvanized pipes)  can also rust out or clog up as the rust on the inside is very rough and catches hair, grease,  and other debris and will eventually need aggressive rootering,   which if the pipes have rusted enough may open up holes in them.I should note CAST IRON (hub and bell) old sewer pipe,  at least the 3" and 4" stuff seems to have a bit longer lifespan than galvanized steel;  it still rusts but doesn't crumble and flake and encourage blockages like steel does,   so an old house with a cast 4" sewer stack you may be fine for many decades more if you just replace all the branch lines going into it but leave the main stack.   

He also had gray hair and a few decades under his belt.

Again I am playing the REALTOR hair because I have my license, however a wholesaler would just communicate to a licensed real estate agent of what to say when an offer is given to them.  

I hate to pull the grey hair card but 20 years of collecting rent is 20 years, how many years have you been handling rental properties?

and they come in 2 types: the old 1920s which have great cur appeal, but are expensive to work on and the 1960s which are much more economical, but look like a shoebox. 

This may seem like it's splitting hairs but I assure it is not, it's CORRECTLY setting the stage of comprehension, as what comes next will give this clarity. 

Listen to http://biggerpockets.com/show65 so you can see how I lost money and have more gray hairs than my age because of a having 20 tenants like yours in a 30+unit building in a war zone of Cincinnati.

It is the rare pet owning tenant that properly cleans the tops of door casings, inside heating vents, along the edges of baseboards, and a hundred other places where pet hair and dander gets caught, so you can generally count on needing extra cleaning. 4.