Selling my "old" iPhone 4 - How do I activate it without the SIM card?

I got my iPhone 4S today which I'm really happy about and now it's time to sell my iPhone 4 that I am replacing. It is on iOS 5 and I just erased it, but when I go to set it up, ideally so it's like an iPod Touch, it keeps telling me I need a SIM in it to activate it.

I don't want to sell it with the SIM nor have any data pulled from the SIM onto the iPhone...is there any way to activate this thing without a SIM? Or is it actually safe to activate with my old SIM and then just remove it while not leaving any phone number or info behind? Thanks!

mloffa said:

When you ever sell any phone, you do not send the sim card to the buy under any circumstances! That is YOURS! Just pop it into the iPhone, you should be good to go.

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Sorry if I wasn't clear. I am not going to sell it with the SIM card, but I do want to activate it so it's basically like an iPod Touch when the seller receives it.

Can I just activate it with the SIM and then remove it when selling?