The second question is: was it hard for you to convince him/her?
We started doing freelance projects together and about 5 years ago we decided to quit our jobs and do this full time.
We're still at it :)
At this point we're more like brothers than business partners. Best decision ever.
I met Andrew (my co-founder) through some school friends and hired him when I was running my team at a digital agency (I was 18 he was 16) after 4 years of building platforms together we moved on and setup on our own. Feels like my brother a lot of the time and that's what makes it easy. The ability to be straight with each other when things don't work out but also have a mature relationship where you know where business is and that it doesn't compromise your friendship.
We have complimentary skills (he's more of a PM and business guy). I think I was the hard one to convince :P . I've actually let him down, I'm not pushing as hard as we can and it's stuck at the side project stage (need 50 to 200 more dev hours and I'm the dev).
He actually has beta testers lined up (and willing to pay).