I would invest if you
a) had 1 working prototype (hence they don't sell premade, fully functional Bitcoin ATMs, yet

)
b) could get this arms-length agreement to multiple retail locations, in writing
c) had a rock solid plan to tackle the legal issues
d) you could prove you had some other type of collateral to recoup my investment, if the "ATM as collateral" idea goes south
d) elaborated further on you and your partner's backgrounds/experiences
Robocoin and Lamassu seem to be moving right along with this same concept. If you're serious about it, I'd get started on it ASAP
Good luck!
