Thanks for the feedback Jason. It's good to know this is a legitimate fear, and I'll certainly work on the clear upfront communications to mitigate the problem.
I'd advise spending as much time as possible, and trying to work together on some smaller projects before making the plunge.
Oh, as a minor note, instead of saying "I decided to abort the project as I didn't want to do 80% of the work while earning only 50% of the profits."
I would smooth that out to something like, "After some discussions on the amount of time we were both able to commit, in the end it made sense to stop working together. It seemed like the best choice since I was able and willing to spend a lot more time than he/she was, so we ended up parting ways amicably."
Assuming of course, that is what happened..!