Sewer usage has been based on water usage here in CT for a long time. The costs for sewer are about the same as for water, so your ex wife would be paying a small fortune here. We don’t usually allow separate water meters in a residence, so she would be paying sewer fees on all that water going into the garden.Having public water has its pros and cons. The biggest pro is always having water. The only caveat to that is if the public utility's source of water dries up then you will have water rationing. Not very likely. The biggest con is cost. Even modern houses are not designed to conserve water. I know all about conserving water. I lived on my sailboat for 9 years away from a dock. I had an 80 gallon water tank. I had to haul my water most of the time. 5 gallon jugs of water are heavy. What is the biggest waster of water? Pressure water where you turn on the tap and the water flows. I have a pressure water system on my sailboat. If I used the pressure water system my 80 gallons of water would last 2 to maybe 3 weeks. Using the foot pump the 80 gallons would last 2 months. How much water does it take for a guy to take a shower? 12 cups using a garden spraying.
In the area I just moved to water is expensive. I am anticipating paying up to $100 per month for water. My Ex-wife and her husband live in Paso Robles. They are avid gardeners. Their water bill averages $400 per month.
Not much difference between sewer verses septic other than cost. The biggest difference is not flushing anything other than pee and poop down the toilet and not using the garage disposal when you have a septic system. Toilet paper, etc. and food scraps have to go in the garbage. The cost of sewer is now getting tied to how much water you use. Use more water. Pay more for sewer. Kind of makes sense if you think about it. The initial cost of a septic system is very close to the cost to connect to the sewer in a lot of areas. Once installed a septic system has no cost other than having the septic tank periodically pumped. How often depends on what you flush down the toilet and put through the garbage disposal. I think that my public sewer cost is going to be around $35 per month.
Natural gas verses propane is a wash.
Adding a 5,000 gallon storage tank to a low producing well and using solar to run the pump solves the problem of a low producing well.