Everything requires maintenance at SOME point, but I consider this to be maintenance-free.
Everything you see here is used stuff, so it wasn't terribly expensive, but even used, this stuff isn't exactly cheap. Our total materials cost for this build is around $3000, and will provide enough power that we will never be connected to the grid.
Minimum requirements for a smaller build are a battery, a solar panel, a charge controller, and an inverter. Prices vary widely on these things, depending on what you buy, but you could probably put a basic system together for around $500.
I'm currently working on a series of posts about the builds like this we do. They should start appearing in Off Grid Community this coming weekend.