This is to use your Nexus 5 as a wifi hotspot on occassions when no wifi is available for your laptop or tablet but your cellular data plan from T-Mobile is working and that plan is the cheap one, the T-Mobile $30/mo plan, which dosen’t work with the Nexus 5. (The Nexus  4 will do this without modification.) You would have to “root” the phone. I recommend Nexus Root Toolkit (NRT) to root the phone. Then you have to modify a file in the “root” directory that tells T-Mobile that you are tethering (and would prompt you with a popup to pay them more money if you are using the Nexus 5). You also have to change your APN from ipv6 to iv4/ipv6. I know this all sounds like gibberish. This post is not a “how to”, just a statement of a workable path to accomplishing this task. It can be done and didn’t take much time THIS TIME.