Should I provide my guests with bottled water or a Brita water filter or leave it up to the guests to bring their own water?

Appears the guests may have left the faucet "on" when the pipes were frozen and when no water came out, forgot to turn it "off".What may have caused the overflow of the sink is maybe the drain lines were also frozen?

Its generous and I don't think anyone would go over it with normal usage. 

Water overflowing the sink, seems more plausible than some missing caulk.  

Water from the well has sediments and water forms a yellow lining in toilet.

If they can't do that, keep shopping.This may require digging up the foundation, sealing it from the outside, and installing a french drain to keep water away from the walls.

Can fix the water damage in the basement yourself.

And I will state different jurisdictions have different rules, processes, expectations, etc.In my area you are required to have a permit to swap a water heater.

For one you can't limit usage.

Water meter-water company.