Trying to get a sense of a project's scale/timeline/cost

We need to design and implement (w/ a hired programmer) a workgroups/community-style web app (in PHP/MySQL) with calendars and forums, on the scale & complexity of PostNuke (which I think is brilliant). I know that there are programs out there that already do this function--I am looking to design something very specific from the ground up.

I realize that PostNuke is a fairly mature program that has slowly evolved, but what if I were to make something on that scale from a complete functional spec.

My questions are:
1) How long would something like this take?
2) How much would something like this cost? (I realize there is a pretty big range, but what kind of bid would be suspiciously low--a novice--and what kind of bid would be too high--ripping me off?)
3) Other than money, what other incentives are coders willing to take (now that no one expects startups like this to go public in 5 years)?
4) What would be your process in selecting a programmer? (is there a FAQ on this? if not, there should be)
5) For large projects such as this, what kind of payment installments. I wouldn't pay up front, but I also wouldn't hold out to the end.
6) What can you tell me about NDAs--efficacy, how often you sign them, do you take them seriously, how early in the interviewing process are you willing to sign one, etc.?

Since these are gray area questions, I welcome as many conflicting answers and opinions as I can get. Thank you.

so you want to reinvent the wheel?

i don't have much to contribute to this but when you say a programmer do you mean "a" as in only one? do you honestly think one programmer would achieve this before you die?

i can't say for sure but the cost would be great. if you hire a programmer it would likely be based on wage (hourly). that starts to add up over the years.

is the money coming in from this going to supercede the money that will go out (will you make money from this)?