You will need an SSL cert. To get an SSL, you need a CSR (Certificate Signing Request). On IIS, this is very simple to do. An SSL Cert is usually purchased yearly. No monthly fees unless you are using a shared SSL cert. Usually the hosting provider needs to generate the CSR to be given to the SSL provider.

You also need your own IP address since the it will use port 443 (https). If you can generate your own CSR, you can buy your SSL cert from any company, like GeoTrust, Verisign, Godaddy, etc.

If you are going to be testing it locally, etc you can get a free SSL from www.cacert.org