Advice
iPhone 5 will work at 4g ( non LTE ) speeds on t-mobile. I heard somewhere that this requires refarmed areas.
I think there was one version of the iPhone that was Lte compatible and it ran on channels 2 or 4 or aws?
I had a verizon iPhone 5.. It ran fine on tmobile at 4g speeds in San jose, California
It wasn't lte, but the speeds were almost 9 Megabit which was faster then the LTE that verizon offered in my area.
Unlock the phone.
Once it is unlocked, and you want to double check if your iPhone 5 will be either 2g,3G or 4g, buy the "simple mobile " SIM card from Amazon. It sells for 1 cent and it should tell you what speeds you will get without investing any money
Or signing up to any plan