It m ight help if you explain what you mean by a "partner". It's a vague word, that could mean different things in different contexts.
If you mean that you want someone who you can delegate your content-writing to, then that's what you should ask for. You'll get a better response if people know what you are looking for.
Assuming that is what you want, I personally wouldn't bother with the likes of Craiglist, or similar sites. A competent freelance writer does not look for work on such sites. I would start by asking around for a personal recommendation. If that doesn't work, search for someone advertising their services in your area. And if your budget runs to it, consider approaching an agency.