Are you working on a Mac or a PC?
What exactly are you looking for the software to do for you?
There are so many facets to a haunt, especially a "pro" haunt that you may find that you will have to look at several programs to cover all of the bases. Some of those programs may already bee on your computer.
Agreed - SketchUp (now carried by Trimble Surveys after Google sold it off) is the go-to software and its free to boot. I suppose there is some learning involved but having used it since v.4, it has become second nature to me.
There are some other third-party add-ons you can use to animate your creations or stand-alone software to render SketchUp models as well. My avatar was created in SU and rendered in Vue (I have unfortunately lost the original full size rendering, so you can't see all the details, but it really does do a fantastic job of creating photo-real). Vue is expensive, but from what I see of SU Podium, it does as good a job for much less (note Vue does do a much much better job of creating "real" landscapes...).
SU has some rudimentary camera "fly-by" animation capabilities, but SU Animate allows for animation of the model components themselves.
Like the others said, with a few third-party software options you can really create your haunts in the SU environment. We (HauntDesignKit) are currently working on our own features and apps for SU made just for haunters!