Echoing the sentiment that a single speed cargo bike is a terrible idea! It's a lot more knackering than riding a normal bike. Plus as people have said, a gear low enough to get a fully loaded cargo bike moving at a set of lights is going to be really spinny once you're up to speed. The alfine hubs we have on our work bikes need very little maintenance, apart from the occasional tweak when they start to slip, you just forget about them.
Echoing the sentiment that a single speed cargo bike is a terrible idea! It's a lot more knackering than riding a normal bike. Plus as people have said, a gear low enough to get a fully loaded cargo bike moving at a set of lights is going to be really spinny once you're up to speed. The alfine hubs we have on our work bikes need very little maintenance, apart from the occasional tweak when they start to slip, you just forget about them.