Galvanizing copper is a chemical impossibility.Projected lifespan of galvanized piping is typically projected at 60 years, but it can be less or more depending on the water quality of the source.Copper is generally projected at 80 years but same caveat.Lifespan of plastic is for all practical purposes, infinite. 

@Bryan Sowieja  well not a popular thought but its realistic.having owned a bunch of rentals in Mississippi we get some pretty large tenants in those areas.And special toilets are required along with reinforcing sub floor below.. and they can wreak havoc on plastic tub shower combos... can't comment on if you can exclude them. but if you rent to folks that you know are quite heavy no matter there physical type  IE professional athlete  power lifter.. cage fighter  WWF or whatever... you do have certain realities in the bathrooms that need to be addressedI have had more than one 400 lb plus tenant have the toilet give way on them during the act. 

Is PEX the same thing as pvc; if so, I thought we couldn't mix copper with plastic? 

If my buyers see pre-formed plastic on the floor they assume the entire place is junk and pass.

(C) Buy those adjustable plastic grids from the big box stores and cut them to size and insert those green filter into them? 

We have to remove the cover, drape plastic underneath the unit to guide the cleaning solution and rinse water into a trash bin.

I sprayed them down with some water and gently lifted them up, trying not to break them apart, and sealed them up in plastic bags. 

The parcel with the arrow and above and below the arrow are ALL owned by this company.http://www.polydeckscreen.com/They are some kind of plastics manufacturer.  

So adding on a kitchen and bath may literally require whole new plumbing because mobiles used old style plastic cheap stuff that rots away and you can't fix or add toi. 

Replacing cabinets is something you can do yourself if you have the ability to get the cabinets into the space.If the countertops are a straight run, you can also find inexpensive plastic laminate counter tops and install those yourself.I hope I am not overselling something as being easy when it may not be.