I use Maya, but I wouldn't suggest starting off with it. It can take a long time to learn. There are several free software's out there you can download and use for free Blender being the best. Still blender can take a lot of time to learn, but now is maybe a perfect time to do so.
https://www.blender.org/
Google Sketchup is probably your best bet. It's the simplest to learn and it's quality and tools get better each year.
https://www.sketchup.com/