20 inches deep or wide? if its a wide shallow closet, then get a 250 watt hps, put one or two mother plants in one side, with room for a few clones under CFLs, and a small flowering room with extreme ventilation on the other.
if it is a narrow deep closet, make it a flowering room. grow your mothers and clones elsewhere, or maybe use autoflowers.
either way a closet that small will not be turning out poundage. go for small fast turnover plants, remember to save some space for drying!