Navigating a big RV through cities and parking

I've been researching getting an RV for awhile, actually going back and forth between just buying a truck and trailer instead, and try to visualize what it would actually be like driving and owning one.

We are planning a cross country trip, and while we are primarily sticking to truck routes and old highways, we'll certainly be passing through cities and wanting to visit the nightlife.

But the more I read about it, the plan seems to just be parking at Walmarts or Costco, and crossing your fingers you can find an available RV camp site. It seems rather restrictive, which is ironic considering the whole point of getting a motorhome should be to set up shop wherever you want and sleep in your vehicle. Going to fast food places or trying to park at downtown areas just seems like a nightmare. It also seems like every little stop requires extensive planning to make sure you can turn out of there if needed.

If it seems like I'm using the word SEEMS a lot, it's because I'm asking for advice from experienced travelers. I love the idea of owning an RV to take the family on adventures, but don't have any friends or family who have ever owned one before.