Putting together a stage system

I'll be blunt with you,  the words "decent" and "$500" do not go in the same sentence together when it comes to PA.
 
I'm not saying you can't pick up something second hand that would do the job for that price, but it won't be the quality you're expecting.
 
If you can be a little more specific about your needs (number of channels, type of instruments, room/audience size, expected PA size, etc) then I can give you a list of what you need that you can pick from.

When you say a set of speakers...  
 
You have 3 choices.
1) Passive speakers, an amp, a mixer.
2) Passive speakers, a powered mixer.
3) Powered speakers, a mixer.
 
From what you're describing I'd recommend a small powered mixer and a pair of speakers.  Don't forget you should have stands for the speakers for them to work efficiently.  If I point you in the right direction I'll leave it to you to choose exactly what you want based on your budget and your better knowledge of what you want it to do.
 
It would be very easy for me to say you need this, this and this and then you find its not loud enough or whatever.
 
Gimme 20 mins.

I'm curious about the second option you posted- What actually does it imply, do you have to chain two together, then control volumes separately? Seems like a little more work 
 
So I'll be on the lookout for 12"-15". I'll definitely look for things I can try out at locations... Think I could find used ones that are bigger or better?
 
Thanks, Karyn!

http://www.sweetwater.com/store/detail/EON610
Don't know about the inputs on that, but reasonable price.
That is a Class D amp, new kind, I forget what that is all about, but since the wattage is so high, then I suppose that would be enough. See if a mixer plugs into that, and get a $100 mixer whatever, perhaps whatever anyone sells. Stands probably cost more, and all the cables and any of that stuff, which will add to the price. But there are other ones also. - 10dB down probably on low end and perhaps on high end. How much down, well, that maybe be a concern, if you like deep bass or really high highs that probably most people can not hear. But probably works fine, using mixer bass and treble control (or midrange) whatever.
 
12" speaker (one) with a mixer that puts out either mono or stereo (if you want another speaker later on. (no stand if angled on floor or with a stand for the speaker. (or the 15" speaker one but that to me be too much bass.)
??
 
http://www.sweetwater.com/shop/live-sound/pa-speakers/
Well, I suppose there is something there, I think you can figure it out.
Or at a local store, or ZZSounds whatever or Musician'sFriend or another one of those on-line places or at a local store GC whatever. Wherever they sell any of that PA stuff (musical stuffings).
 

spacealf
http://www.sweetwater.com/store/detail/EON610
Don't know about the inputs on that, but reasonable price.
That is a Class D amp, new kind, I forget what that is all about, but since the wattage is so high, then I suppose that would be enough. See if a mixer plugs into that, and get a $100 mixer whatever, perhaps whatever anyone sells. Stands probably cost more, and all the cables and any of that stuff, which will add to the price. But there are other ones also. - 10dB down probably on low end and perhaps on high end. How much down, well, that maybe be a concern, if you like deep bass or really high highs that probably most people can not hear. But probably works fine, using mixer bass and treble control (or midrange) whatever.
 
12" speaker (one) with a mixer that puts out either mono or stereo (if you want another speaker later on. (no stand if angled on floor or with a stand for the speaker. (or the 15" speaker one but that to me be too much bass.)
??

Bare in mind that's an each price, not a pair.  And the lack of inputs would require an external mixer with related connecting cables. + stands,  you'd be looking at $1000+ for a working system.
 
Still good value, but double the budget.
 

How many people and what size of building will the PA need to accomodate?

If you have some good woodworkers in your church, I HIGHLY recommend building BFM speakers. They can be made for a fraction of the cost you would pay for professional audio products and will be some of the best sounding speakers you will ever hear.
 
http://www.billfitzmaurice.com/

I would not know what they rent if anything. The only Sound Reinforcement System is at the Blues Fest in the Summer, and that thing fed back a lot of times or else the person running the sound could not adjust it, despite all the computer and speakers and board whatever it was. I did not look at it at all, just noticed the fed back and the sound going down almost 3 city blocks (not large city blocks either).
 
They may rent what they have, but for $250 you can get one speaker (PA speaker which is PA - not Sound Reinforcement System which is larger with mics on everything) but then I am not buying it, so I doubt they rent just anything if there is a place to rent any PA system in the first place.
 
Only reason mentioned the new JBL PA self-powered speakers is because the coverage is it seems it more than twice as much or about the same for one speaker vs. two speakers of another manufacturer there looking through the pages.
 
It use to be at one time, building some wood cabinets and sticking in 2-12" radio shack speakers for a PA system (two speakers cabinets total) which is all that could be afforded (not self-powered though - passive speakers). It sounded okay though I guess. Well, who knows, probably was days feeling good from the booze and the distortion in Rock&Roll whatever it was.
 

 
Renting a PA may depend on the area you live in, whether it is actually just a PA or like I said more of a Sound Reinforcement System.
 
http://en.wikipedia.org/wiki/Sound_reinforcement_system
which in the end costs way, way, way more.
 
There is also college courses on sound engineering or acoustic engineering with calculus and other subjects (and probably no guaranttee of a job afterwards like - recording studio like a Sound Engineer.) The professional side gets blurry with all the home equipment out nowadays to have people do it theirselves, or make a name for theirself whatever.
theirself - means - he/she/space-alien type fuzzy hairy ugly biological meat creature that can talk and act in the galaxy or universe. ( somewhat humor there).
 

Probably not too good.
http://www.radioshack.com/samson-expedition-xp150-portable-pa-system/3200064.html#start=3
 
 

Here's another option you might look into. Check with other churches in your area, both for the expertise they may bring to the table and the sound systems they may have available. It is not uncommon that as a church grows, it outgrows its current equipment. New equipment is purchased, but the old equipment is still very usable.That equipment may be re-purposed, sold to help cover the cost of the upgrades, or donated to help other churches.
 
For example, when we moved from our portable gym setup to a new permanent sanctuary, the new setup was a combination of existing and new equipment (60-channel mixer). The mixer we used in the gym (28 channel) was re-purposed for doing recording. There was a need to continue using a portable system, so a smaller mixer was purchased (12-channel) and we purchased a small portable lighting set. We use that portable set around the church for various functions, and occasionally 'take it on the road' to support other churches and their events.
 
My suggestion is get to know the tech crews at the other churches in your area, attend a few worship tech conventions if possible, and let it be known that you are looking for equipment. You might be surprised what is available.
 
Hope that helps