If the other person in the proposed partnership cannot demonstrate equivalent-value skills and equivalent previous success in critical-to-the-business areas where I'm weak (or uninterested) like sales, marketing, biz-dev, enterprise sales, acquiring VC - then my answer is almost certainly going to be "Sure, $8k/month is my usual rate - discounts of 20% for 3 month or longer block bookings. When would youy like me to start?"
If the other person refers to themselves as "An ideas guy!", my rates double, and require 50% up front.
Software development is serious time consuming and often difficult work. Do not ask me to do it for less than market rate without making it very clear that you are going to work just as hard with equivalent skill and experience to make the idea succeed.