What’s your plan for cleaning between guests? 

I inspect my own properties once a year, I try to take care of the things that reduce later damage like cleaning the gutters and servicing the furnaces.

Full paint and flooring (including removing some wall paper and glued down laminate flooring), patched holes in walls, replaced cabinet doors that were missing, replaced a few lighting fixtures, reconfigured closets that were missing hardware, cleaned up back yard.

They can't clean it once in a while?

Very easy and makes everything just look neat and clean in a way that you can't quite put your finger on.

upgraded floors, bathrooms, cleaned it up.

We added flooring, cleaned up, added windows, gutters, kitchen, bath, and we always do something a little bit over the top in the deign.

I completely agree with Account Closed  "We won't be able to renew your lease after xx/31/xx." with a reminder that they are still responsible for last month's rent and if they leave the apartment clean and damage free they will receive their full security deposit back after move-out.No reason to go into details.  

Try and buy from who would inherit property.You should consult an attorney if your goal is to end up with a clean title.I personally would get the rightful family member to Quit Claim it over to me and rent it forever.

we pay them 20% of the after tax income excluding cleaning fees.