I have found that modular homes are pretty reliable as long as you work with a builder who communicates well. The biggest benefits are the speed and consistent build quality, factory conditions really do make a difference. The only hiccups I’ve seen usually come from site preparation or delays with transport and setup. If those pieces are handled well, the whole experience ends up feeling a lot smoother than a traditional build.
Here is the another discussion that will give you information: Developing RV sites on raw land - #4 by AFlanagan