Though hard disk is cheap these days, ssd is still expensive. My Android SDK is taking something like 14Go.
I have installed apis 19,20 and 21, and each is taking around some valuable space (21 uses 9Go!) in the
You will need 19 and 20 only if you plan on creating projects targeted (compiled) for those versions. And you most probably do not ;-) Also, avoid downloading everything each release offers if you do not have a specific need for all of them.