We had a meeting with the rep from CENYC earlier this week and got some great news about the potential for rainwater harvesting in the garden; chiefly, there is a downspout on our neighbors building that is literally flush against the two properties and perfect for a simple, easy to install 1000 gallon tank.
Also, if our neighbor landlord does not want to work with us and the CENYC -- which unfortunately seems to be the case -- then we have devised a plan B that will result in a 350 gallon tank and a new retrofitted roof for the deck and shelter next to the tool shed.
Plan A is the ideal when it comes to harvesting rainwater from an adjacent rooftop but I wouldn't hold my breathe... either way, after years on the CENYC's waiting list, we're going to figure something out.