If you were to come to me and say "Hey, we have this idea, we have a prototype, and we'd like to make it a product. We'd like to get it in front of investors an

If you were to come to me and say "Hey, we have this idea, we have a prototype, and we'd like to make it a product. We'd like to get it in front of investors and make you a partner. We know you are going to put in a lot of time and effort to build it. We can offer you 33%, as we're both going to take 1/3 ourselves..." I would not be offended by that. That is actually a very fair assessment and a good starting point for a fair negotiation. As for splitting equity that is a bit more of a complicated conversation. Not all equity is the same. In a fair world you might say: 10% reserved for employees, 20% for investors, and 70% for us. That seems fair on the outside right? You would each get 23.3% and you could each outvote any investor you bring on board. However, often times you don't have straight equity deals when raising funds. You might take a convertible note. You might have an investor who will only accept preferred shares of equity with special arrangements. Even relatively simple and underfunded start ups can sometimes have very complex cap tables with multiple levels of shares of stock being given different rules and right. If you're not careful, the cap table can easily run away from you. I have known quite a few successful entrepreneurs who have gotten screwed in the end, not because of co-founders, but because the cap table went sideways. For example, one small start up was offered north of $80MM 4.5 years after starting up. The co-founders each, after taxes, walked away with a few hundred thousand. So, to answer your actual question, it really depends. Getting a partner who has been through those whole ordeal before can be priceless.