Instead of InDesign a better choice if you are just now purchasing would be framemaker which include RoboHelp. RoboHelp is reported to make clean customized ePub and the latest can create ePub 3 as well.
Most InDesign threads are in the ePub forum. I suspect most users watch both of these forums but ePub is likely to be more on topic and there are already quite a few threads there.
Dale
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