paint isn't as durable as powdercoat...
and powder coat isn't as durable as you'd think.
You can paint them but without a durable clear the paint will get scratched easily and you will get chips.
Powercoating is much more durable but as KJ points out won't withstand being curbed or a moron tire installer.
If your looking to do it cheap, mask up the tires, scuff up the wheels with 3m scuff pads and paint them your color choice. If you want some added durability throw a few coats of clear on them. You could do this in just a few hours and for $40 in spray paint and masking materials. If it doesn't last you can always pony up the cash to have them PC'd.
If your going to send it out for paint you should just go strait to getting them powdercoated. The price difference isn't that much at that point.