In the past (some years ago), parked domains could be a good way to get residual income. You bought a good domain nome, setup it as a parked domain and spread backlinks to it in several websites. Therefore, you could get some good search ranking for some keywords and your “website” would get organic and referrer visits.
But it isn’t working properly now, because search engines get to identify if a domain is parked or a real website, so your parked domain doesn’t get organic traffic, and many websites are combating all kind of spamming, so you won’t get to create backlinks in popular websites. In a brief, it’s unlikely you get good money just parking a domain.
And, in the last years, domain registration is more expensive, what becomes even more difficult to get enough money to compensate what you will be spending. So no, I wouldn’t recommend you to earn money parking domains. But it doesn’t mean no one is making money from it. People with very good domain names can get some traffic still and traffic is gold, always. Thus if you can get good traffic for your parked domains, you can try it, ok?
Conclusion: I wouldn’t spend money trying it, but if you are good to get traffic from websites (and we are talking about 30K monthly or more), so you can test it, ok?