Why don't you do what Commodore did when they announced the Pet? (As written in 'On The Edge: The Spectacular Rise and Fall of Commodore')
That is, take the payment up front with the promise to deliver in 90 days, then use it to actually make the machine! According to the book, when they started taking orders, they only had a few prototypes and hadn't started production.
Seriously, I will be willing to pay (some) money up-front as a deposit. Ideally, I'd like one Minimig already built, and one board (so I can see if I am competent enought to build one myself!)
:-)
