You can't paint one side without it bleeding to the other usually so your best bet is to agree to paint a side each and split the cost of the stain.
Then again you might find like in our case that you own the fence on e.g. the left of your garden and your neighbour owns the one on the right
Cheers. That explains it.
We've got Cuprinol for the fence and the posh Ronseal for the shed.
Debating how to approach it with my neighbour on one side (we are responsible for the other two sides).