I have been in the land business so have not had to deal with tenants, toilets or cockroaches.

Looking for recommendations for a deep shower pan, or a pan with a substantial curb/lip, so that I can hang shower curtain instead of doors.

Simple repairs can take a $2 part; like the flapper in a toilet tank, the outdoor porch light, or the batteries in a remote. 

The idea would be to not take the calls for the leakinf boiler or toilet but also to expect them to have a big list of vendors for the repairs that charge a fair price and not take advantage of these costs of repairs.

I apologize this answer is a bit vague however there are definitely a lot of scenarios on how each particular home could pan out. 

When we opened the cleanout it was ¾ full, but it still flowed out when we ran the faucets or flushed toilets.

Everything has been fairly uneventful with them - except for having to replace the whole HVAC system the first summer they were in it because it failed (not their fault) - and they do take really good care of the property, they get along with the neighbors, and have even fixed a couple things themselves - like a leaking toilet.

Is toilet paper included, food, drinks, etc.

Not all of these kinds of projects have (or will) pan out. 

Tenants, leaky toilets, landlord/tenant laws, debt, etc. all for 3%?!