Got news on the second lot their water well came in over 2x gallons per minute.  8 is ok.  

A thousand gallon tank, which would be about the size of a small-to-average septic tank, with a cabin with 2-4 people staying, is likely going to fill up in less than a week unless they've piped the grey water (washer, shower, kitchen sink) somewhere else like a dry well.

We have about 9,000 gallons of water storage under the house.

We also kept or installed underground water capture systems for about 6mm gallons of water.  

This will reduce the heat inside by 20 degrees immediately.  5 gallons can cover 2 1/2 container roofs.8. 

Gas $10 per gallon. 

When we had a large dog it was my kids job to pick it up , he did and put it in a 5 gallon bucket , he did that for a week , then it rained . 

@Mario Morales  one running toilet up to 200 gallons a day. curious what else you find.

My boilers use between 2000-4000 gallons of oil a year which is $6000-$12000 a year.

Water shed is important for the longevity of any foundation, the quickie math is 1 inch of rain on a roof displaces .6 +- gallons of water.