I'd like to add that this is a very risky investment. You need to guarantee that your friend will supply you with electricity for 15-18 months. If your friend changes their mind or something breaks down, your equipment won't mine. Who will pay for the losses?
Yeah you are right FP91G, like I always say having constant power supply is very important in mining so just like you said he needs to be sure his friend will supply him with electricity for months and it should also be constant power supply.
Concerning his friend changing his mind what if he tells his friend that they should go into a written agreement, I believe with a written agreement his friend won't just change his mind, and I believe his friend is not doing all this for free he will also want some share from what has been mined out.
It is a good thing the OP decided to bring this here and I believe with all the reply he has gotten he will know the next thing to do and I believe he has already taken action or decision because this thread was posted since April it's been 6 months now.