There are viruses for mac too, just not nearly as many. And unless you plan on going to porn sites, software crack sites, etc., then you wouldn't have much to worry about. I've got a couple studio computers connected to the internet and in the years they've been online, haven't had a single problem. You can also run software to block 99.9% of that stuff.
There's no way I'd waste my money on a mac these days unless I absolutely had to. It's reign in the pro-audio world is over.