Can i hook up an iphone that was on a locked account?

My iphone 5 was on a sprint account with an ex who didn't pay the bill so the account got locked. I had to get a new phone and i new sprint account. I was wanting to sell my old phone. I completely erased my iphone 5 and i was wanting to sell it to a friend but i'm worried when he tries to hook it up will they not let him. I'm afraid they will see the serial number and see it was on a locked account.

Your friend will not be able to activate that phone under their account. It is now blacklisted in Sprint database (until the bill is paid in full). As of now, blacklisted iPhone can't make phone calls, or basically be used as a cellphone.
I guess your best bet would be try selling it for parts. Check eBay.