I'm the founder of my current startup. The new startup is an opportunity to leverage my industry expertise twice. I would get shares in the new startup, but not have control. Obviously the idea would be to create a close partnership between both startups (they are quite complementary). I'm afraid of two things: 1/ This new startup may become a direct competitor one day. The industry is very big, with the largest player having only about 5% of the market. Still, our two startups are two of the very few players with an innovative concept in the industry. 2/ The insights that I transfer to the new startup, may spill over to the rest of the industry more easily (as I have little control), reducing our competitive advantage. How could I craft this partnership so that my two fears can never materialize?
1. If they are providing you a significant portion of equity and salary. Look at it as an acqui-hire.
2. If you have revenue and are growing then perhaps your evaluate the opportunity differently ask have them buy your company out.
3. If you want to stay on your own then stick to it. Don't worry about the competition it just motivates you to stay ahead of them.
4. If you really want to work with them and have your own company. Create a JV (joint venture) you have a lawyer work through this to iron out all the details.
If you want to talk just give me a shout.