Haha, well, I'm going through a "divorce" now with a co-founder and unfortunately, it costs money, time, and effort to try to get my assets (code) back. He was never able to generate a dime of revenue after I brought the code, but now he wants the code (which I want to open source).

So yeah, in many ways, it is just like a marriage when you formally create a company with a co-founder. Don't do it unless you need to and if you do, make sure that you can get your assets back if you are bringing existing assets to the table.