He wants me to run with the idea but he wants (and deserves) something for the idea. Has anyone been in this situation before and how did you solve it: a small amount of equity? cash outright? He mentioned 5% equity. That sounds reasonable but I thought I'd ask here.
My test for deciding if you want to bring an 'idea man' along is this:
Imagine that you and your friend -- the idea man -- work together at a nice day job. You both make a good salary. One day, your boss tells you that he wants to fire your friend (who wouldn't take a pay cut) unless you're willing to take a pay cut. Your have two choices: (1) take the pay cut, or (2) your friend gets fired. How big does that pay cut have to be before you let your friend get fired?
For me, it's less than $1,000/yr. I love my friends dearly, but I'm not going to pay a buddy just to hang out at work and keep me entertained.
Unless your friend's idea is going to make you wealthy enough that you no longer have to work, then you probably don't want to give him 5% of your company just to be your friend.
Otherwise is a complete zero. I personally have ideas for 10 lifetimes of work and that is just the top which I don't scrape after a brief analysis.
As others said - ideas, in their initial states, rarely worth anything. Experience shapes idea into an unrecognisable state and even the right ideas, without the correct offering, may fail.
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Sometimes an idea can be worth a lot. Image a working company in a bottleneck situation on their concept. They have a problem that blocks their scalability. If you bring up an idea, that will fit their situation and be an elegant solution - they this can be worth a lot. But this requires a tremendous experience in the field.
If I'm going to give 5% of my company to someone, it will be to my very first Dev who built V1.0 for very little money to build out his portfolio and because he liked the "idea". Without him I would never have had the opportunity that I do today.
http://steveblank.com/2010/01/25/whats-a-startup-first-princ...
http://www.businessmodelgeneration.com/downloads/businessmod...
If your iOS app is just relying on the App Store as its channel, and the coding involved more than just writing to spec then maybe it's worth more than 5%, but the main value is in finding the spec, not coding it :) - if part of the value or the main part is having a good execution and user experience, it's also likely worth more than 5%, but it's maybe better for a VC-backed startup to just pay employees.
For example, If the idea is "A better battery." Nothing. If the idea is "A new doping scheme using recent research in unrelated chlorine molecules that can drastically improve lithium ion battery life" then the person deserves equity.
With that said, you are considering investing in the idea, so that means you think there is some value in it, at least to you.
Offer/give what you think is fair. If it makes you feel more comfortable, maybe do 5% up to a preset maximum?
If he continues to be involved, even in just an advisory capacity, I would think about issuing him more shares over time -- you might argue that at that point he's starting to provide product management assistance, or call him an advisor.
http://sivers.org/multiply https://www.youtube.com/watch?v=QgaBvEO2LYY
The original idea will inevitably morph into a completely different thing.
Edit:
If you must give something ( because it strikes your fancy) , then ensure they are non-voting shares and that he cannot prevent any ( and I mean any) amendments to the by-laws, shareholders agreement or the articles of incorporation. ( to the full extent of your laws)