We are looking to buy a property that we'll rent out for additional income. If we do this we'd be the landlords, so is it a bad idea to invest in a property with a septic tank. Are septic tanks a hassle?
Septic tanks normally need very little maintenance. They may occasionally need to be pumped if they are used heavily, like if there are many people living in the house. I've lived in houses with septic tanks my whole life. You probably shouldn't use bleach often, as it will reduce the level of bacteria that break down the waste. I flush Rid-X into my spetic tank monthly to maintain the bacteria. It's pretty cheap insurance.
Generally the only problems I'm aware of relate to sending things down the drain that shouldn't be (e.g. excess cleaners that can kill off the bacteria, lots of grease/oils that may clog the drain field lines),and too much or even too little waste going to the system. ...or the drain field being damaged/compromised in some way (usually trees taking root).....
Fundamentally a septic system relies on bacteria to break solid wastes down, and the drain field releases the liquids (and water-borne solids) to be filtered through the ground releasing the water back into the environment. ....so really the problems tend to be killing/starving the bacteria, or clogging the system. ..... generally not too much of a maintenance hassle, but I'm no pro either.