Can an unlocked iphone 4 work on virgin mobile?

I just want to make sure i have this right before i order the phone.
I'm trying to get an iphone 4 for virgin mobile, i know the iphone 3gs dosen't work for virgin mobile because it isn't CDMA. But the iphone 4 is CDMA, right?
i found and iphone 4 on amazon for $420 instead of the full price of $550, it seems like alot to pay but in the long run it will be cheaper.

A permanently factory unlocked iphone can be used to any network e.g vodafone, orange etc. There are many stores there to provide unlocking services.

I would suggest:

You can consult with GuaranteedUnlock Team.
They are a mobile unlocking webstore-www.guaranteedunlock.com.
Their service is brilliant. Support 24/7, safe payment gateway they use is paypal so you don't need to worry. Just ask them at support@guaranteedunlock.com

Hope they will solve your problem.

Best of Luck