Half the time it does not really need to be replaced its just the inspectors opinion.. but on the flip side its common for investors to buy properties that check out fine in the home inspection run water and and flush the toilets a few times.. but when property is put into service boom there is an issue with a tenant there and your obligated to fix it.. 5k is on the low side for these replacements. personally if everything else checked out and you can get the seller to say pay 50% which seems reasonable I would close on it then you know you have a bullet proof rental. you just lost your inspection fees  your appraisal fee's etc.. now your walking and going to have to pay those all over again on the next house you want to buy..

For old bathtub surround tile, we've been using a product called duma wall you can liquid nails or sika it right over the old tile so long as it is reasonably flush.

Do you have tens of thousands of dollars to throw away or flush down the toilet? 

She’s flushing mask PPE and booties down the toilet!!!!

As for ARV, I run comps for clients all of the time and I have never taken sewer VS septic in to consideration- people just expect their toilet the flush.

Go in each unit and flush the toilets, you will hear of the water is still running if it’s the toilet flapper.

Here are a couple of thoughts for you from a renter's POV. 1) make sure it has an actual flushing toilet.

Start with basic things about the home: check plumbing-turn on taps, flush toilets, look under sinks. 

I've had one tenant try to intimidate/bully another (a woman about your size, against one upstairs that was quite a bit smaller, with a small child) over noise (yeah, ok, her kids get up early on Sat to run to eat and watch TV and yes, upstairs people do have to flush toilets now and then).

Otherwise you may just flush all your SFR money down a money put.