That's a big pass on that tree, tell them they need an insured professional. If they're tight on money just have them pay someone to get it on the ground and tell them you'll handle the rest.
I wouldn't touch it without some iron clad, lawyer approved permit and release from all the property owners. Even then, I wouldn't do it unless I was confident that I could do it properly. If it can be shown that you made a bad choice, you have a lot to loose. It is up to the tree owner to get all that together. Maybe he should go to the town to see if there are options, rules, etc.
I've cut down a few trees at other people houses around neighbors land with power lines and fences and such. Although I did OK, I am by no means a pro, and I don't climb. That being said, at this point in my life and with liability laws and lawyers getting worse, I'll pass on stuff that isn't out back with no chance of property damage. There is easier wood out there.