Too low?? Not at all. In fact, since you will be feeding it, that is super. Easy to start and easy on the yeasts.
Nothing above 1.010 is too low but if you did start at 1.010, I would call it a yeast teaser. Some would call it a yeast starter and it is not very practical. Your starting SG of 1.070 is fine and more than adequate since you will be feeding it.
Joe