Call a local septic installer and ask them what the typical range is for a 4 bedroom house. Mine in King county is about $31k with design/install.

Call a local we’ll driller and ask them the typical cost for a well in the area of the property you’re looking at. Mine is about $30k with a nice pump house and water system.

If it’s PSE and they don’t currently serve your property and they have to run a “line extension” that’s on them but the transformer and running to your meter is on you.

I know grays harbor county allowed owner installed septic systems in the past.