Usually store bought apple juice is around 1.05 to 1.06 out of the bottle. If you add concentrate or sugar the SG will go up. Like JPNJPN said it depends on what you want the finished product to be. Sweet, dry or somewhere in between. Seems like with cider it's whatever floats your boat. I prefer my OG to be around 1.06 and my FG to be around 1.005 and then back-sweeten.
This is super subjective and will vary a lot form person to person but I typically follow this:
1.005-1.009: Semi dry/semi sweet
1.010 and up: Sweet
One thing to be aware of is that as a result of apple varieties used some ciders will be much 'fruitier' than others. This aesthetic term is different than sweet which can be measured in SG but fruity ciders can typically be drier in terms of residual sugar than non-fruity ciders yet still seem to be on the same level.
I agree with LeBreton. I happen to like mine 1.015-1.02 because I love sweet Also love apple juice flavor. There's many that would say that's too sweet though. Woodchuck is at about 1.02. I think also the ale yeasts like Nottingham and S-04 leave some fruitiness in the finished product to go with the sweetness, as opposed to wine yeasts which strip out alot of flavor. Hope this helps!