What should I do if I cannot afford a PA System for my band?

Me and my friend started playing music awhile ago. I used to sing and play guitar and he would do back up vocals, I would sing and you could hear it over the acoustics. Now me and several of my friends are working on starting a band. however we are still in school so we sometimes have a hard time finding time. However we still practice often. Now we are using a drum set and using electric guitars and a b. It tend to get very loud and you cant her our vocals and I even have a hard time hearing myself. A few of my friends (not in the band) told me that if I get a band together they could get a few decent gigs for us. Here's the thing though. Were not sure if were ever going to make it that far, it might just be a jam thing. I've been considering lately that I would run out and pick up a few microphones, stands and instead of using a PA use PA to amp converters and use an amp of some kind, it would cost a lot less. Then if we decide to just get a PA system we have a spare amp and we can just use the microphones for the PA. Is this a good idea? Any suggestions?