Ask HN: How do I reach a fair agreement with my co-founder?

Hey HN, I need your advice. I'm re-negotiating equity stakes in my start up and want to be fair to my co-founder but don't see his long term role in the company. What should I do? At the beginning of this year I participated in a hackathon with two co-workers. One of the guys is a web developer and techie like myself, and the other is a database admin and project manager with no programming background. We built a pretty cool web app and won the top cash prize at the event. We decided to use the cash to continue improving the app and were accepted into an incubator program over the summer. At that time the other techie guy had to stop working on the project because of a new job. So my co-founder (the db admin/project manager) and I went through the incubator program. I was working part time 2 days per week at our old job and 3-5 days on the start-up. My co-founder was working 4 days a week at our old job (where he is a minority shareholder) and 1-2 days a week on the start-up. After graduating from the incubator program I decided to quit my job and work on the start-up full time. My co-founder is continuing to put in 1-2 days per week. Now we're at a crossroads. We've got the product to a point where we can start selling it, and we've both been talking with potential customers and investors. Sales is neither of our strong suits and we agree that we will need an experienced CEO shortly after landing our first customer and raising additional money. I envision my role as CTO and doing primarily product development, but am having a difficult time imagining what my co-founders long term role will be. He is not interested in sales or the CEO position, but can't do any technical work other than database design and maintenance. We've been renegotiating equity stakes because we are rasing a small amount of angel money to keep the doors open as well as bringing on a subject matter expert to help with improving the product. I know this is all pretty vague, but I wanted to get your advice on the situation. I'm asking him to drop down to a <10% equity stake if he's unwilling to start full time. He can't be full time now because of other financial responsibilities, but I'm willing to wait until we can raise some money to pay him. Maybe this is a mistake... I don't know that his full time involvement is what the company needs right now. I've talked to him about my concerns, but I get the feeling that he doesn't agree with me. The conversation didn't really end in any sort of agreement or mutual understanding. Am I being unreasonable? On the one hand I want to be fair and I doubt the company would exist without his involvement. I've done the solo founder thing once before and wouldn't do it again. On the other hand I don't want the company to have a bunch of equity held by anyone who isn't working full time or 100% dedicated and even if he were, I'm not sure what his role would be. Has anyone gone through a similar experience before? Any suggestions for how to evaluate the situation in a fair way? I am stressing out about this and would really appreciate advice.