Ask HN: How to structure a partnership

I'm a freelance web developer, and I have built up a sizable business. For some time I've been looking to either hire help or bring on a partner. So far I've only worked alone, and occasionally hired contractors for overflow.

Recently I've found someone I'd like to partner with. He is a former coworker who now freelances. The difference is, he is just starting his business (no clients) and mine is fairly established (many clients).

I am open to giving him part ownership in my business, I just don't know the right way to structure things. I have built up a large business with a good reputation and I have clients knocking down my door. He is bringing another set of hands to the table, but no clients.

I should add a few things: This person I'd like to partner with is someone I've known and worked with for years. I have no doubts about his abilities or work ethic. He has the exact skill set I'm looking for, I know he is a talented developer and I know we work well together. Essentially, he is a perfect fit. I also trust him completely and want to make sure he is fairly compensated.

I think together we can grow something really great. I'm just looking for some advice and ideas on how we can structure our relationship. I'm open to anything, traditional or not.