The catch. Said rich old dude is very eccentric. He doesn't hire street sams or troll body guards to guard his compound.
For some odd reason, most of my "eccentric" ideas tend to revolve around the un-augmented. I find that, to really spook players? Having a very well-organized group of mundanes who think fast on their feet, stay in constant communication, organize intelligent surveillance and security rounds, have set up alternate routes of retreat -- people who really plan for a potential invasion? Yeah, those people freak the hell out of players.
Using unorthodox, for me, sometimes means tossing in a whole lot of misdirection. Like micro-speakers Kleen-tacked by potted plants, on a fireplace mantel, in the frickin' toilet; the odd drone that comes around, all blinking lights and weird sound effects that I'll hope they follow instead of shooting down (and which invariably leads them into a damp, cold, cell); the kid or woman's faint voice heard sobbing over there that turns out to be a recording and leads into a booby-trapped cellar (landmines, or concussive grenades, or stuff that's a lot of flash and bang without necessarily being deadly, but whose detonation will trigger an alarm); a corridor that gets pumped full of Nitrous oxide (laughing gas), just to kill away their stealth and turn them into a riot of easily-detectable hilarity.
Why? Just so Eccentric Man's security can get the drop on the Runners. It's fun, keeps everyone on their toes, and really doesn't need to be exceedingly expensive (even if, we assume, Eccentric Man ought to have enough nuyen to hire a SWAT team or two).