Thanks in advance
You will need a contract for them to provide you with certain amounts of water,
You' probably want to specify minimum amounts and whether it will very based on season etc,
Its highly likely you will be expected to pay a share of the capital and on going operational costs of drilling/running the bore....
Go and find a rural lawyer, there will be plenty of precedent in the area
Don't be a cheapskate, get your own bore. Especially as since he wants consent for his bore, say that you will agree at the same time as he agrees to yours.
By the time you pay for a lawyer to write up a proper contract. Which would have to include things like payment of costs, service level required etc. Yet your property would be more valuable with it's own bore, instead on relying on the neighbours bore. While your neighbour's property would be less valuable, if it is subject to a requirement to supply water to others (you). And that is even assuming that the council will even allow 1 bore to supply more than 1 property. Would they count such a situation as commercial and charge higher fees? Your costs would likely be similar to just getting your own bore anyway.
The council might change the rules in the future, and refuse to allow any new bores, impose extra consent conditions etc.
Having reliable access to water is a major selling point of rural properties. Money spent now on a bore is likely to increase your property value.