How long should I let the concrete set up on posts?

...should you help pay for it? My situation is different. My neighbor is asking me to help pay for a fence. Truth be told, we need a new fence there, but the problem is that the land at the fence is about 4 feet taller on his side then mine. This creates a problem because dirt from his property tumbles into mine. And where the ground is stable enough to put a fence is about 3 feet on his side of the property line. My intent, is to make a barridcading wall on the property line and put a fence there. I can't afford a new fence or a wall right now as I have low income and other diy projects that are more important. He doesn't yet know how much the fence will cost (apparently his son-in law builds fences and will do it for him). He threw out a number of 25$ a month to help pay for it, but my wife and I don't really want to pay: We don't need a fence right now, we have better plans for that area anyway, and as much as we want to be good neighbors, we can't seem to justify financing improvement on his property. I plan on helping him work on it, but I can't see a financial incentive for us to pay for it. do most neighbors split the costs of a fence?

OK, I am 99% complete with my new cedar fence. I went to dig my last post hole which is next to my house and found that there is a drainage pipe about 10 inches down which runs along the foundation of my house. I live in a new developement and decided to see what my neighbors are doing with their fences and discovered that most people are mounting a 2x4 to directly to thier house and attaching thier fence to that. I think I want to do the same thing but I am not sure how to go about this given that I know that my fence does not allign so that I can attach this 2X4 to a stud. Should I be concerned with this? Any suggestions on what to do? I have the same problem on the other side of my house where I want to put a gate, in this case I just need to have a post attached to the house to hold the latch for a gate. Thanks!