SP Sizing math?

So keep in mind I don't have an SP background. I have a client who has this idea of getting into the SP business and I'm trying to help them realize, realistically, what kind of undertaking this will be.

For a residential SP, what is a good reference for general guidelines on sizing. Such as, for 6,000 residential users, how bandwidth upstream would be required to be fairly assured your phone will not be blowing up with complaints? What amount of oversubscription is acceptable at what amount of bandwidth? Are customers just sold if you tell them 5 meg down, even though you have a 20:1 oversubscription?

I have read in NANOG archives 100Mbps/1,000 users for a school campus environment; would residential be equivalent?

Any input would be greatly appreciated.

Thomas Magill
Network Engineer
Office: (858) 909-3777
Cell: (858) 869-9685

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San Diego, CA 92121

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