Co-creating with someone to run an RP (or SG) is not uncommon, and you can see this especially with very advanced ones. I, for one, haven’t tried it yet, though I am about to experience being a co-owner with the upcoming Meraki Coast cough totally not advertising cough with some of our raddest forumers here!
So, @RPers…
woah you’re really close with Nil 
I’ve done it on RPs and SGs before and I only recommend doing it with someone you know will remain active.
I don’t know why, but, suddenly, my subconscious is telling me to go check that out
I also pretty sure I haven’t unless you count my friends and I just making up random things that happen in an RP cause we all have equal control XD
I have! Technically I was the original creator of CHB (I co-created it with an IRL friend, but she went inactive and I was the one behind nearly all of it anyway) and then Ani (@katabasis) became a co-owner as she started giving some amazing ideas and wound up completely helping make the plot. So, by the time CHB was first revamped with Siren’s Cry, she was definitely a Co-Creator helping make it from the beginning and has done such an amazing job, (now to where some people even forget that I’m a creator too).
You have to be careful with who you create an RP with. You have to know what you’re each doing, are you both creating the plot, or is one of you just helping with signups/fcs/managing things. If you’re doing it with someone you know you can count on, it can make for an amazing RP. You have each other to bounce ideas off of, when one of you isn’t certain about something you can look to each other, and it can allow the rp to go on even If you’re temporarily busy. However, if you both aren’t on the same page then things can be complicated, and if only one of you has knowledge of how something is continuing then if they can’t be available for a time then you’re stuck. Then, sometimes you can be co-creating an rp, and the other RPer isn’t necessarily reliable and can drop out on you/become inactive.
I tried many times to create an rp together. But my frantic brain and need to control keeps me from allowing the other person to put any imput.
Its not that I don’t want people to help and give imput… I’m just too scared the concept moves too far away from my vision.
Yess Meraki Coast 
It hasn’t started yet so there’s still time, but I can’t wait for it to starttt
i have!
i actually started out by helping with RPs like The Broken Utopia and Fairytale Forest, both of which were made by a group of people (mostly inactive now so rip)
also Exousía (my fave RP ever) was a group project with some of my forums best friends (@pomme and @Ataraxia)
well, in my case, it’s been with some of the RPers i get along best with, and we were familiar with just screaming bouncing off ideas before we started planning an RP together, so -while this depends completely on the chemistry and relationship you may have- i think a big benefit from my experience is that ideas flow better, and you get to develop them with people who are just as excited as you are
also, one of you may notice mistakes or details you didn’t catch, making everything neater; or ask questions you hadn’t asked at first, thus helping you develop the ideas better
and being a team also helps a lot when it comes to organising things, since more people can keep track of different stuff, it’s easier to keep everything neat and organised
and well, as everyone has said before, it’s complicated if you aren’t in the same page as everyone in the group, but i think, if you guys communicate well, that can be solved
I wish!
I think that having someone to co-create with your RP is actually great, especially if you have no experience in running one before. You can ask someone for ideas, opinions, and other things concerning your RP.
I also think that it will be more effective if you find someone who you are comfortable enough with or have just the same interest in your RP as you do!