So I just bought a duplex in south fl with 70 ft of dockage on the water.

We'd be looking for a smaller cottage, preferably not too far from a large body of water, ideally sub $200k.  

Recently in my quarterly visits I like replacing the hvac filters, run some diluted chlorine down the ac drain line, the water is very hard so I recently started running some drano down the lines.

There should be demolition/existing condition plans, site grading, roadway plans, water/wastewater/storm, and detail sheets. 

Ended up renting at 1600 with tenant paying all utilities except water with a one year lease.

3 hot water heaters or 1?

Maybe you could create a spreadsheet that has some plumbing/other construction quotes and some "what if" parameters- such as "if I found a house that has 2 bed/1 bath + kitchen/hot water heater, generally how much would it cost the plumb the whole house with new copper/PEX and a water heater".  

The power bill and water bill would be their responsibility along with any repairs going forward.

I am purchasing a mobile home park 5.5 acres with 7 occupied slips in place, sewer septic, and well water.

There is a lot of water intrusion into the basement in heavy rain.