I agree with the sentiments (and warnings) above.
I DO, however, have one apiary where a couple of the hives are "owned/managed" in a shared fashion, and it has worked out well for the last couple of years.
I had a friend/customer who bought/buys my honey to use in the production of his own end product. He had a prime forage location, and asked me if he bought some hives and put them there if I'd manage them for him. We talked about several alternatives, but in the end, here is what worked for US:
He bought two complete hive kits from me (brand new, same manufacturer and same specs as I use. I bought them unassembled, put them together, wired the frames like mine, painted the boxes, and provided the stands - charged him just the "assembled" price as listed in supplier catalog). I also procured the nucs that we used to populate his two new hives.
He also agreed to let me place a certain number of my OWN hives at that same location. This is only 10minutes from my office, so its convenient for me to go work them on a long lunch break... While I'm there inspecting, etc my hives, I work his two into the mix. When we harvest honey, he helps out, and we segregate his boxes from my own. He owns the honey from his hives, and I own the honey from my hives. If his hives don't produce as much honey as he needs for his business (they don't, nor will two hives likely ever produce as much as he uses in a year), he has first right of refusal on the purchase of the honey from my hives at that apiary. I just keep it stored and labeled independently of my other apiaries. Additionally, I store HIS buckets of honey and drop them off to him when he needs more.
All in all, it works well for us. He gets to help and learn, he gets a source of honey that is HIS, I get an additional great location for some of my own hives, and I have a built-in buyer for the majority of the honey that comes from that apiary. We agreed that if HIS hives need anything (hardware replaced, treatments, re-queened, etc) that I'd procure and supply what is needed at cost. Last season I did end up moving a couple of frames of stores over to one of his hives from one of mine to help it out, but just did that as a friendly gesture as I would do for almost any friend or good customer.
We both believe that time-permitting, he may be able to take over the management of his own hives in a couple of years (if his schedule allows it).
Not saying that NOTHING could go wrong in the future, but since we both clearly expressed what our intentions and goals were, and talked about many potential hurdles in advance of this "partnership", we have not run into any speedbumps yet.
Ralph