Another potential area of concern: Your neighbor can just decide to stop paying the HOA fees--and short of taking them to court, you have very little recourse as to how to collect. They could also decide that those roof repairs aren't their problem, since they're on the lower floor--again, what can you do short of taking them to court? There's no Condo Association or Board to enforce the bylaws or provisions of the Master Deed. It's just you and your neighbor.

That said, you could also end up with great neighbors who follow the agreed-upon rules.