It make sense if you have to replace stuff anyways but not so much if its an upgrade to a working piece of equipment. 

For $20 you can buy a kit that replaces all the working parts of a toilet. ie everything but the ceramic parts and the seat.

I used PBR Construction out of Revere on my triple decker in Eastie for removing and replacing all vinyl, wrapping the windows in aluminum, and replacing decking/railings on the porches. 

Also, don't forget to ask the contractors for suggestions/ways to be cost effective in replacing the roof. 

When I closed they didnt even have keys to give me, I had to kick in the back door(needed replaced anyways).I wouldn't worry about plumbing unless the house is on a slab.

I had to send them receipts of the big ticket items like the roof replacement, windows, replacement and some before and after pics.

Just because a contract died (Could be buyer lost job, neighbor gave an even better offer then backed out, discovered there was a leak in the H2O tank and they replaced it).

For insurance , typically 2 layers , asset replacement insurance + liability insurance = Total insurance .. 

But with most properties, things happen, and this month she had to replace a toilet and a water heater that took almost all her profit.A lot of people in the city use the local insurance carrier that is much cheaper than the big boys.

In my area it is $6 sf to remove and replace LVP.