What do you want to do 2D, 3D, BIM, interiors?

SketchUp was originally designed for the Mac then Google bought it. You must buy one version or the other but the files are interchangeable. There is a version that is free and a professional version for $500. No software is better for designing the exterior of a house or creating a 3D rendering at any price. It is getting better at producing 2D contract documents even though it was not intended for that purpose. There are a lot of tutorials on YouTube.

Chief Architect is not written for the Mac but it can be run on a Mac by using a Windows simulator like Apple's Boot Camp. The cost of the full version of Chief Architect is about $2,200 or $1,500 for the "Lite" reduced feature version or much less for a student version that is the full version but leaves a watermark on the printouts. They also publish Home Designer that has 6 different versions from $60 to $500. Home Designer Architectural is $200.

I can't tell you much more about consumer level CAD; I've never used any of it except the Pro version of SketchUp which is indispensable for architects.

Always try a free trial version before buying any CAD software. The learning curve for much of it is staggering.

If you just want to design, and not CAD, then also just consider an online program: www.floorplanner.com is one that gets bounced around here every now and then. It works to see, if you are not a spacial person. It has some limitations (I've only used the free version though, so not sure if you pay if those limitations are still there).

Anyway, maybe worth looking into for your playing around with a design, before you take to a real architect.