Even with further information, it'll ultimately have to be what both of you are comfortable with.
Granted, you've done a lot of hard work single-handedly but do not underestimate the value/importance of implementation, especially in a startup environment.
Also, if you all are going to need/raise funding, you should give some consideration to the currently prevailing norms of founder - co-founder ownership patterns acceptable to the funding sources and keep that in mind while deciding on this.
Until now I was working as part of research for term projects, now as a side project. I am sure I can get traction without any investors, until I get some users on it. So it's a side project for both of us, we both have full time jobs. Can you give me some numbers? 70-30 or 80-20 split?
From purely an investor's perspective, I believe the more even a split, the more attractive it would be.
However, since you're not seeking funding at this stage, I'd say it is pretty much your own call - between the two of you. Have a frank discussion, try to work out what value you've built so far and what he brings to the table and go from there. I'd say anything, 80-20 / 70-30 is okay, as long as both of you are comfortable with it.
Even with further information, it'll ultimately have to be what both of you are comfortable with.
Granted, you've done a lot of hard work single-handedly but do not underestimate the value/importance of implementation, especially in a startup environment.
Also, if you all are going to need/raise funding, you should give some consideration to the currently prevailing norms of founder - co-founder ownership patterns acceptable to the funding sources and keep that in mind while deciding on this.
HTH