I just noticed this thread. I have never heard of any parking service that allows advertising of parked pages. So I checked Parked.com's terms of service, and here is a quote from their TOS:
"Permitted, compensated traffic can originate from two sources only:
1. type in (direct navigation) traffic and
2. existing search engine results/expired traffic.
All other types of traffic including bought traffic, traffic driven by PPC campaigns, traffic directed from hyperlinks are not permitted. If your traffic originates from any sources other than type-in and search engine traffic, you will not be entitled to payment as per this Agreement. Regular checks are carried out and we reserve the right to suspend any domain from our Service at any time, on our sole discretion, if we reasonably believe that you have violated this Agreement; for example, if we suspect that the traffic on your domain is bought, generated or redirected in any way that contravenes these terms and conditions."
So Parked does not allow this either. They may not catch you right away but eventually they'll figure it out and at that time they will most likely shut down your account and confiscate your unpaid earnings.
Then there's the Google issue. Google is really cracking down on people who use Adwords to drive traffic to pages that consist solely or primarily of advertising. You might get away with it for a month or two at most, but when they notice it they will at the very least "Google-slap" you, in other words they will drop your quality score into the pits and raise your minimum bids to $5.00 or $10.00. If you've done this before and have been warned, they might actually suspend your Adwords account.
Yes, it's possible to make a lot of money in a short period of time by doing arbitrage to parked pages, but just be aware that you are violating rules on both sides and when you get caught you will be burning your bridges with the parking service and with Google.
So don't do it. You'll just have to earn your money the old-fashioned way like the rest of us: acquire domains with natural traffic, or work with affiliate programs, or build actual content websites.