4 years ago we found a similar size house, but bigger lot on Winnisquam. As said, anything waterfront, not shared less than 600k is a bargain.
We had to replace the septic before we could use it, it was totally failed. This. website has a lot of good info on it. It's not the easiest to surf but persistence pays off.
https://www.des.nh.gov/organization/.../ssb/index.htm
I found a property I was looking at had an approved plan, but never an approved completion of installation. But we were told the system was new ?????
The site also helped in deciding on a designer and installer as you can look them all up. You can also search by address.
Good luck,