Ask HN: Friend-sourcing actual work (not just asking advice)

I have some grand and ambitious ideas for a new service on eMusicTheory.com, to really add some fire to the normally tedious process of learning music fundamentals. But to build this thing, I need help from music teachers (among my customers and friends already), people who've studied music pedagogy in depth (among my friends), fiction writers (I'm married to one and have lots more among my friends), and probably some development help (again, excellent resources among my friends and colleagues, and hello hackers).

I can get advice and feedback for free -- that's super. But what I want to do is write up my plans in detail, then invite friends (and friends of friends) to come look at it, give me feedback, and claim chunks they'd like to do in their spare time... for which work I'd overpay them once the minimum viable version is launched and bringing in revenue. ("Overpay" because of the delay, and the smallish risk... worst case it would flop, and I'd pay them very slowly out of the normal site income). Fortunately, the work involved is primarily fun and interesting; I'll do most of the boring coding aspects myself.

So: has anyone tried this? (Is it a good idea?) AND how best to organize it, coordinate the work, and lay out the framework in a way that people can comment on it easily? I'm also torn between making it invite-only (to avoid random not-really-qualified people showing up and wasting my time) or just making it open (and easiest to use!) and figuring obscurity will protect me from the hordes.

[I should also add -- I will ask my accountant about what's involved in paying people, 1099s, etc. but suggestions about handling that simply are also welcome.]