I don't even like flat on the ceilings hardly.  

Could not see much because the basement is literally filled to the ceiling with model trains, VHS tapes and thousands of baseball cards. 

If you have sufficient ceiling height, a good option is to install a resilient channel system and 2 layers of 5/8 type X sheetrock.

For a 2 story, see which way the joists run, pull up the wire to the second floor and run over to the ceiling light for the first floor by pulling one floor strip. 

It's allowed me to do some of my own work like changing toilets and fixing leaking ceilings, but even if I don't want to do a job personally hopefully I'll have enough knowledge to not let a contractor over charge me, or recommend something I don't need.You'll also meet local contractors, and hopefully investors.They may offer an employee discount too.

Ceilings need to go too, but floors are fine except for a few problem spots. 5,000 sq ft.  6 kitchens, 6 baths, and about 35 total rooms, closets, hallways, etc. 

The house has 8 foot ceiling on each floor. 

My bedroom ceiling started leaking...I put a pot on the floor to catch the water and called the landlord at 11PM.

Gives me hope there's a high ceiling, not Austin-like but enough upwards momentum to keep me happy.

Suppose, for example, the tenant delays in reporting the leaking roof - then you've got mold, damaged ceilings, etc.