I give 400BP and some free stuff: ([Charisma + Intuition]*3)BP worth of Contacts and the following free skills at level 2:
- Computer
- Data Search
- Dodge
- Etiquette
- Infiltration
- Perception
- One of Blades, Clubs, Pistols, Thrown Weapons and Unarmed Combat
That way they have at least functional competence at the key bits of being a shadowrunner (based on the stuff in Runner's Companion). If they want to buy the relevant skill groups, they get an appropriate discount but have to buy them up to level 2 to start with.
So the most any player in my game started with was 492BP, and the least was 474BP.