If you are worried about ethical or legal concerns in running a presale in your current situation, just be very upfront with people the same way you are with us. Price yourself at a point where the people who take early risks can see 100x (or higher) returns "easily" given your understanding of the market and your business. People are willing to put money into a 2 man team with a dream, but you might have to lower your expectations of how much they are willing to put in.