Another problem you might face is any relatives of Greg. With no corporates structure - or even one that just says 50:50 you may see wives/parents/cousins convinced that all startups are going to be ebay looking for their billions. Remember the saying: you only choose a spouse - you don't get to choose their family.
You may find you spend another few years working on your own to make this idea a success and then lose it all to the legal fees defending against multiple claims of who owns the other half.
It might be a good idea to make a break and restart the idea with just you.