Second - you'll need a septic....homebuilt w/55 gal drums is perfectly fine, but won't pass a real inspection.Third - You need a propane tank for cooking, heating water, etc.... just haul in 100 gal tanks and swap the out yourself....or get a 300 gal tank from a company and have them fill it every 3 mos.Fourth - A couple solar panels and a few batteries for lights and charging like you saidThis is not cheap nor is it easy, but it is fun.

For a permanent install, though, I wouldn't use them as they are battery operated.

We are out of state so we would be interested in 2-4 units most likely but purely from an investment standpoint, as opposed to owner-operator. 

lol, hate to be mean but those guys are pure wannabe. 

Delivered in August 2019.Solar water heater and solar electric panels on the roof (inverter type, no batteries) with feed back into the grid.Update, after 3 years we refinanced in 2023 and added a pool.

Generally i know people hedge for 35-50% at pure maximum for expenses.

Does anyone know of battery powered ones?

Much better than flying solo with a pure FSBO...

Pure profit. 

If you're using an FHA loan, I think you'll have to live there for a year as a primary residence.As a pure investment, it doesn't look very appealing.