Hi Anthony. I agree with most of what has been offered here...but I'll get my 2 cents in as well, having gigged professionally for about 18 years, and now retired from performing publicly.

For acoustic instruments and the human voice, nothing beats Bose speakers....especially an older set of 800s or 802s...These speakers as amazing as they sound are somewhat inefficient however and require at least 250 watts of power per side...so you'd need a decent stereo power amp that pushes a total of at least 500 watts...These speakers are fairly light weight and packup into small suitcase-like boxes once they're protective covers are on...and mount on top of lightweight, adjustable telescopic-style stands....Most major music stores that have a p.a. department would know exactly what I'm talking about...

Small Electrovoice Elite speakers work well too, and may be more readily found. You'd need a decent 12 - 16 channel mixing board, enabled with a separate monitor mix section, and you'll need a few good floor monitors and a separate power amp to drive them, that will also feed into your mixer.

I'd suggest renting with the option to buy, until you find exactly the right combination of equipment to suit yours and the other musicians' needs. Either of these speaker systems will cut up to 500 people no problem.

Build whatever the cost of your p.a. rentals are, into the purchase price you charge your clients....so figure whatever it is you need to pay the other musicians, as well as what you want for yourself, and then add the p.a. rental cost that...If the places you are playing want you and the band badly enough, they'll pay it...and monthly p.a. rentals shouldn't make or break the cost of hiring your group. They are a necessary part of gigging.

Renting the p.a. will also provide you with a 100% tax write off, if you are deriving any income from these gigs, as well...and the advantage (like anything) is that you are not locked into anything long term...Just go month to month or week to week, depending on the frequency of gigs...and use this p.a. system in rehearsals as well so you know all the ins and outs of it. Best of luck.