Do I have to set up a source channel before I can create a deal?

No. Source channels are optional, and they exist purely for attribution: they tell you where a client came from, such as the Apply Now button on your site, an ad, or a specific referral partner. You can create a business, run matchmaking, and submit to lenders without ever setting one up. Your unique signup link works out of the box, so if you just want to start sending clients in, share that link and come back to channel setup when you actually want the tracking.