First, hobie 16 is not too bad to single hand, but make sure not to flip it, because being 17 you're probally not very heavy, and I couldnt right it solo (at 175 lbs) and probally need a minimum 200 to be able to do it).
$400 is not bad, but what year is it? Are there any soft spots? You can find plenty of old boats with softspots everywhere for that price, but I recommend you try to find one with few soft spots, preferrably none.