Difficulty of adding or enlarging a cistern on a house for sale?

and where did i say to be wasteful?

if you want to take a bath, take a bath. if you cant get your cistern enlarged, you might have to replenish from time to time through a water delivery service.

You can buy lots of water for the cost of building a cistern. I've got friends that are life long islanders. They make it fine with a 5000 gallon cistern. They have lots of plants as well. They flush the toilets and take showers everyday. They just aren't wasteful.

if you want to take a bath, take a bath. if you cant get your cistern enlarged, you might have to replenish from time to time through a water delivery service.

You can buy lots of water for the cost of building a cistern. I've got friends that are life long islanders. They make it fine with a 5000 gallon cistern. They have lots of plants as well. They flush the toilets and take showers everyday. They just aren't wasteful.

Actually I was referring to your post as valid, just adding a little more information. The wasteful part had nothing to do with what you said. You can take it any way you choose I really couldn't care less.

We are building a 650 sq feet house. It has an 11,000 gallon cistern. At this point I would say $3 gallon is too low, double that is probably about right. I will say that it seems like the overall costs for concrete construction is about $1500/yd. This includes materials and labor. Bear in mind that this is on Water Island, so we have some added ferry costs etc that you don't have on mainland STT.
Probably a more important thing that was mentioned is that you can have a huge cistern, but if your collection area is too small you'll never fill it up. Here's a calculator that I used:
http://rainwaterharvesting.tamu.edu/calculators/

My neighbors have 5-6k gallon cisterns and they run out of water a lot. I don't think a daily bath is realistic unless you're only living there for 3 months/year or so.

We are building a 650 sq feet house.

That's a pretty small house for a 11,000 gallon cistern.

We do OK with a 600 Ft Sq cottage and 400 sf of gallery space with about 10K gallons. Water saving everything and conservation with 2 people and a garden.