What does your singer sing out of?

Having not played with an amplified singer since school, where we used the equipment their, my Brother and some mates who have been jaming now want to sing.

What do we need to get the singer loud enough. Playing out of our old little guitar amps isnt loud or clear enough.

Are PA's expensive and a must?

We have a decent Mic but what does everyone elses singers do so they are heard against the guitars and drums?

Man when I used to do the sound for bands we used a 1K PA and that was just loud enough. I think saving up for a second hand PA is a must as the last thing you want is crappy sounding / missing vocals !