No parking company will make you rich, unless you own it yourself.
You should only ever use a parking company for the purpose of parking a domain until you have time to develop it. If you make some revenue, then its a bonus.
Domain parking will never be a sustainable source of income, the secret is to park and see what domains do well, then its time to develop that site.
Little example. G*********.com is 100% free games site and has about 5 advertisers, in the last 3 months the site has generated sales for the advertisers in excess of £18,000 ($35,000) of which I get 10% commission, it also earns min, $20 a day with adsense. The traffic is not huge but on average 1300 games are played each day and its mostly UK traffic. Now that is a sustainable income and increases the value of the domain 10 fold.
Parking programs make more money from you than you do from them, with the exception of 2 the rest are dishonest and suspect.
Just read about all the crap we have to endure from programs like SEDO and it will put you off parking for life.
Remember Parking should only be temporary.