1) can, but soft volume cos lacking preamp.
2) not "amplifier" , amplifier = preamp + speaker cone , preamp (like a small mixer with xlr input will do)
3) rock vocals maybe, but ppl use it mainly for instruments like snare or guitar cabinet.
if vocals only try SM58 someone selling at $80 2nd hand @ the soft classifieds.
4) if a shop sell at $120 brand new. cheap?
i'd say "standard pricing". I bought mine 2nd hand mint condition at $90. sometimes you see those sellers selling a real beat up (used live) for like $50-$70.
regarding recording do read up the "DIY recording FAQ"