It's weird, been reading through this thread thinking I really wouldn't want to GM or play alongside a child NPC in Shadowrun. Was trying to put my finger on why, as I've played alongside and GM'd kid PCs in other systems. Even played them before.
Think it's because the way my regular group plays it, Shadowrun tends to be very amoral and usually has a pretty high bodycount. The runners we have end up murdering people for money, and sometimes chopping bits out of them for further profit. The characters also get pretty screwed over in a lot of different ways... Think, for me, there's a line somewhere and kids involved is somewhere over it. Too squeamish for my own good! It'd really suck the fun out of the kill happy cybermonsters somehow...
Whereas the systems where kid PCs have been cool tended to be a bit more black/white, Good vs Evil (i.e. kill the goblins because they're green).
Guess it's about the way the game is run and personal taste. Think if we played a different shadowrun setup to our usual one it could be good.
Everyones got different takes on gaming and all: So, back on topic:
I'd have thought the street orphan could work quite well - remove the parents and schooling from the equation. Possibly someone in a orphanage or other 'low control' environment? Although that might take some of the fun away from the kid concept.
Perhaps use the dependant flaw - a kid with a parent or sibling who can't look after themselves. Would provide a solution to the lifestyle costs issues? Also a motivation for earning some cash?
For lifestyle costs of hacker living with parents, perhaps they'd need to pay out for a series of phony addresses, signal cutouts and so forth - throw off the tracing software? Don't want family dinner interupted by the Aztechnology goon squad? Figure it would be necessary so they can hack from home - don't want to explain to the parents where they are all the time?