Are the walls plaster lathe, sheetrock, are waste lines cast iron, PVC, do you have toilets with tanks or flushometers?

If in doubt, replace the fill and flush valves on all the toilets ($15 worth of parts each, and less than 15 minutes each to change).

I set up an account with eRentPayments.com and emailed him the instructions on how to set up payments.Also, when we went in to check on the toilet, we noticed that there seemed to be extra tenants (a girlfriend or roommate and possible children) not listed on the rental agreement.

There seems to always be that stuff you don't notice until some one is living in there every day.For example, while I am at the house, before its rented, I run all the sinks, tubs, showers, and flush the toilet with toilet paper a bunch.

Just competing with MLS listed property in most markets won't do squat. 

A dripping faucet that takes a couple minutes to fix, a clogged sink that gets snaked in two minutes, or a toilet that runs that needs 30 seconds to install a new rubber ring on the flapper.

By upgrading the plumbing and low flow toilets and fixures will help neturalize the water expense to add more to your bottom line as well.

These include 1) a kitchen sink with hot and cold water, and 2) a toilet and shower thatis accessible without passing through another occupant’s living space.

I need your help, please.After long term tenants the unit needs full renovation:full interior painting, new carpet, some times new interior doors :)  vanity and toilet. 

Definitely don't want to be fixing any toilets when I'm 87 :)