I took over a neighbours garden a few months ago with a friend. I knew her well, she's a good gardener - much more experienced than I but within a couple of weeks her interest evaporated and I was being left to do everything. I let it simmer for ages then bubbled over one day. It cleared the air and she helped me for a while.

I would share a plot with someone again, but I would go with Flum's suggestions and split it down the middle.