If you're planning to start up again in a year or so, I see no reason to sell equipment that can store. Just my opinion, but you're going to waste money selling off equipment that you intend on buying again later down the road. Unless you're planning on upgrading parts....ya might as well keep them.
Some items don't store well. Heaters tend to get crappy pretty quickly when they're in storage. Don't know why, but every stored heater I've ever seen or dealt with (and it's happened a couple times) ends up with loose connections, condensation or salt creep in places that make you worry about plugging the heater in, that sort of thing.
Powerheads should be rinsed with fresh water and, if they're clogged with coralline, go ahead and remove that first. From first hand experience I can tell you that cleaning old coralline is a PIA. Powerhead impellers should be rinsed separately and allowed to air dry before you reassemble for storage.