Basically this boils down to wanting to keep my players greedy. A lot of classes may figure that they've got their gun and armor what more do they want?

Anyway so I think I'll start giving bonuses to Karma based on lifestyle.

I'm wondering what people would think is "fair" or generally a good idea for that sort of thing.

Sound much like "Play the way I want and you'll get karma." Imho not a good thing. If you want the characters to be exactly like you want them, then play with yourself...

The Karma for Nuyen house rule equates to much the same thing (spend money, gain Karma), but still allows people to roleplay being hobos who are forced to into the shadows because they can't make legitimate money, and all the money they do end up getting simply seems to slip through their fingers.

Otherwise you'll end up with everyone in the party gunning for luxury lifestyle, and to be honest, most runners wouldn't keep running if they were living the high life. Sure, some characters would, and if your entire group is that type, and all agree to it, you could give out extra Karma for higher lifestyles - just make sure the other players aren't feeling pieonholed into spending their cash on upkeep.

Or, you could institute both rules, but make the Karma returns on lifestyle lower (maybe hand out 2-5 Karma to the guy who bought a month of luxury lifestyle, while the other guy who cashed in his 100K during downtime by losing it all at the races or donating to charity gets a full 20 (at the standard 5K Yen = 1 Karma)).