I think it may well likely violate SEC and/or lottery regulations.

From what I read, it sounds like you're running a lottery (buy a square for a chance to win $10k).

Then on top of that, you are calling the $10k an 'investment', which I think means that YOU have to be potentially considered an accredited investor if it's an investment and not a loan.

Aside from that, the kind of business that only needs a $10k investment is also likely to be one that it will be a VERY long time before that business can shake loose $10k of their own to give away as an investment (please deal with the legal issues of doing so)

I seems like a nice idea, fraught with grey legalities that you should probably at least get professional advice on.