Can i use an inactive nano sim card with a sim-free iPhone 5s?

No, that's not true. What you read only applies to iPhones that have been previously activated and now you want to use it without having cell service. You will need some sort of carrier account to do the initial activation of your iPhone. Just having a SIM will not be sufficient.

So no, you won't be able to use your iPhone in any capacity without having some sort of carrier account, even if just for a short time, to activate the phone. You could perhaps get an unlocked iPhone and use it with your current carrier and switch later, but you'll need to check with your carrier as to whether you can bring in a new iPhone without having to extend or otherwise modify your existing contract.

Regards.

My understanding is that you need a SIM, active or inactive, from the original carrier to Activate the iPhone.

If the iPhone is unlocked any SIM, active or inactive will do the activation.

Please correct me if wrong.

Best

You're talking about a phone that's previously been activated. A new iPhone, which what Robert is asking about, can to my knowledge only be activated through a cell carrier and all carriers I know of require some sort of account to activate a phone.

Once an iPhone has been activated, then a valid SIM will allow activation again later to be used as an iPod, but not a new iPhone out of the box.

Regards.

Not until the iPhone has been activated, no. Until the phone is activated at least the first time, it won't do anything other than make 911 calls.

Regards.

Thank you for your enlightening response.

Best

Where did you purchase the iPhone? If from an Apple store, does the

receipt say 'unlocked'?

Only Apple sells unlocked iPhones. Carriers sell phones without a contract, but they are still locked to the carrier until the carrier chooses to unlock them.