This is like asking an employee to use *his* car for your business and only
paying him for his cost of gasoline. We all know that there are many costs
associated with owning a car... Purchase, interest on loan, license,
insurance, gasoline, and repair costs.

Same with a well. Every so often need a new pump. Need costly repairs.
Sometimes need to dig a deeper well because well goes dry. Can have trouble
with bacteria or contamination in water and need to treat it. Can have a
daily limit as to how much water can be pumped from certain wells, etc.

What if your neighbor decides to use too much water and this makes the well
go dry for the day and you are left without water?

What if the well goes dry and you need to dig a deeper well? Who pays what?

What if you and your neighbor are without water because the well went dry,
it will cost $10,000.00 to get it fixed, and you decide you want to wait 30
days before having this done (time to get money or loan)? Can your neighbor
sue you because you are not providing them with water?

What if your well becomes contaminated with bacteria and this makes your
neighbors sick? Are you liable for their medical costs?

What if they don't pay you their share and you cut off their water? Can they
sue you?

Etc.

The only way I would do this is to place the well on a separate electric
meter and install a water meter on the neighbor's line. Also a water meter
on your line. (Can tell who is using how much.)

Then find out how much total water can be used from this well daily. Find
out typical maintenance costs over a 10 year period. Cost to replace pump.
Cost for deeper well, etc.

Then get it in writing (with a lawyer doing the writing) that you or future
owners of your house are under no obligation to provide water to your
neighbor, that you are just doing this on a temporary basis until they get
their own well, and that you may disconnect them at any time for any reason.

Also that you are not responsible for any water contamination by bacteria or
otherwise.

That they are limited to using only a certain amount of water a day and if
they exceed this, you can cut off their water without notice.

And if they are late with their payments, there will be a late charge and
interest charges.

That you can change the terms of the agreement at anytime. That the
agreement is not transferrable to another person (future owners of their
house).

Then calculate the cost of electricity they use each month based on their
water usage and charge for that. Also charge for their share of yearly
operating costs (well drilling, pump replacement, repairs, cost of meters,
etc.), and charge for your time to keep track of all this.

Basically the contract would say you are not responsible for anything, can
cut them off anytime you wish, and they must pay for their fair share of
everything (not just electricity).

Perhaps also state that you are charging them a monthly "connection fee"
which will be paid even if they use no water at all and this fee is not
based on usage. (You would not have to calculate usage every month and they
could not come back at you claiming you miscalculated their usage, etc.
wanting a credit.) You could choose to just charge them a monthly fee and
not bother with doing any calculating if you so choose.