This depends on your specific situation, but once a month is great as it gives your skin time to refresh itself.
Acne treatments cost about $195 on average.
If you're not having a lot of luck with over-the-counter treatments, and you don't want to go down the Accutane road, it could be time to consider skin peels or laser treatments for acne. No one should have to put up with problem skin.
Acne treatments take about 60 minutes on average per appointment.
Your aftercare here will depend on exactly what you've had done, and how your skin responds - talk to your therapist. As a rule, though, you'll want to stay out of the sun, avoid intense exercise, and stay hydrated.