It says i can have 0-3 rare units does that mean that if i hire the cursed company i can only have 3 skellies?

Um, no, that's not quite right. 0-3 Rare means that you can have 0-3 Units/Regiments of Rare troops, and each regiment can be of whatever size is required/desired. The Cursed Company would take up 1 Rare choice (assuming that you're not playing a full Dogs of War army), and can have from 10-30 skeletons in it (including Richter Krueger, the standard bearer, and the musician).

hes right, when it says unit it means a regiment, so for instance i take a unit of noight gobbos thats a regiment or unit. see it's not dat hard