We're interested in a house that has a septic tank system.
The house is from early 70s.
I know it would have to be upgraded but thereafter how much maintenance would it need and what kind of cost would we be looking at?
What could initial costs be? Apart from the maintenance costs what other considerations would there be?
I like your board name!!! You need to give a lot more detail, are you specifically asking about the house or the septic tank and are you sure there is an actual septic tank in situ?
Budget for complete replacement and you may need to do some groundwork around the percolation area(s).
Thereafter the costs and running costs will tend to vary from manufacturer to manufacturer.
There are some threads on AAM about such systems of which this is a small sample.
All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.