I can certainly look into this for you. There are a few things to look at when purchasing a used phone. The first thing to check is who was your friend's cell phone provider? If it was with another provider that you do not wish to have service with, the device will need to be unlocked by that old provider before another provider can use it to give you service. Unlocking a device is a one time $50 charge (with taxes $56.50) and this is often charged via credit card. If the device is unlocked or was with the provider you wish to have service with then this charge does not apply.
**I do wish to note with iphones that to ensure they are unlocked properly, the original owner will need to sync it to itunes and do a Back up and Restore, or the device will not unlock.**
As for activating the phone on the MTS Network you can stop by any MTS Connect Store and get signed up with a new plan and be on a month to month service. There is a one time $40 activation fee applied to your first/next invoice for registering the device on the network as an active service.
Otherwise that's it. I hope this helped answer your question. :D