Teach them just how far they can get on their own with their idea before they even need to consider a tech co-founder or outsourcing.
There is naming, branding, research, competitor analysis, writing copy, storyboarding (if it's an app) wireframes, mock-ups, drawing up contact lists, talking to potential customers - which is an extremely important point.
They need to also show willing to learn even some basic technical skills else they just sound lazy. This doesn't have to include development, there's lots of other computer based tasks that need doing.
Their project needs to be at a point where a decent tech person would say "hey this is pretty interesting, the next big step you're struggling on is something I'd find really easy to implement"
A non-technical co-founder has to have the hustle to build a foundation to even get a tech person interested in talking about it, never mind contributing.
I'd suggest teaching them that if they say "I have X number of people committed to buying this - if only I could build it" is far more compelling to a developer than "I have an idea in my head but I've not acted on it yet"
