I would be a little alarmed if a seller proposed that to me - concerned there is an ulterior motive.  

These systems have ejection pumps and filters and alarms.  

Should it send off alarm bells to a potential investor not to buy a property if the seller claims that he/she does not know the age of the roof, does not know if the roof has ever been replaced, does not disclose the nature of a minor repair to the roof, or what the original material that was used for the water pipes, although some of the pipes were replaced with copper, and if the seller claims that he/she is not sure of the age of the gas water heater, but claims that it was replaced 8 years ago with a major rehab?

There are "poor" landlords and slumlords in all sizes of properties.That said, in our experience, there is the no-mans-land of small multi-unit properties (5 - 20 units, say) where financing will be commercial and, if not a converted house, the property will have the commercial systems one expects to find in larger buildings (fire alarm and suppression, security doors, common boiler, common laundry, etc).  

I'm thinking of things like smoke/CO alarm testing, rekeying locks, or testing the water heater temperature (120 F max in Wisconsin) where you may someday have to prove that you actually did the work, or simply that you acted in a reasonable manner to provide a safe home for your tenants.

Bright lights dawn-to-dusk, motion detector to trigger alarm.

There is a reason we have alarm systems on every Tacoma BRRRR rental.In other words, BRRRR sounds great but show me some local investors doing it consistently here in Seattle.

Frankly, my internal alarm was raised.

Once the alarm is sounded (even if it's a vague one) they have to move on to a different fishing hole to keep scamming.  

Therefore, there is no electricity at the house, and I can't install alarm system.