Michael raises a very valid point. Just to save a few cents per gallon could cost a lot in the sheer frustration of driving through congested areas with a travel trailer. Especially in those places where you plan to just overnight. Not to mention the cost of fuel to get there.
Parking at Walmart and the like is being restricted in more and more cities. When I have asked, I always ask for permission, I have been refused more often than permitted. City ordinances were always cited as the reason. The thought of being roused in the middle of the night, and asked to move on, was not for me. Truck stops do not have such restrictions. They are there specifically for big rigs to park overnight.
Lifey