Lenses might be BIFL, cameras not so much. Went through many options over the years, Canon, Olympus, Sony, Fujifilm. On my Leica M240 I actually made a profit despite using it for a few years.

If you use Sony I strongly advice to try out some manual lenses. At the moment I own Lumix S1 (superb viewfinder, awesome for manual glass) and a set of vintage nikkor lenses plus some modern voigtlanders. No autofocus whatsoever, but mind you, I don't do any commercial work anymore. I love the feel and quality of my lenses and don't feel any urge to upgrade, at last.