If you have a AT& T hotspot how much data can you get for it?
If you can have 5 sim cards per household, then you can get 700mg x 5 = 3.5gigs per month?
The rules are the same for LTE "phone" SIMs & data-only SIMs-- for now, at least, either will work in a hotspot. Moving forward, you're probably safer if you get data-only SIMs, since they're designated for hotspot use & likely to remain exempt from calling needs via the messaging app.
Your math is correct-- minus a small safety margin on each SIM, and assuming you have at least 10 FreedomPop friends. (200mb base plan, plus 500mb from friends.) Most dedicated hotspots do not have a way to set a data limit in the device, so you need to monitor carefully and/or pay to disable auto-top-up.
Some folks prefer to use a phone that has a working native hotspot function as a hotspot, since phones usually have a way to set a hard data limit. Still, allow some safety margin. Not all phones can enable the native hotspot on FP, though. BLU phones can, and I suspect that other budget unlocked phones can as well. I've heard that the factory unlocked Moto E4 and G4/G5 series cannot. In my experience, AT&T Prepaid (formerly GoPhone) cannot.
I've seen warnings that the SIM slots aren't really designed for constant swapping, and you may damage one from swapping a lot. Some of the AT&T hotspots have an external SIM door, which is handy for swapping. (I know the Unite 770S does.)
Most phones will work with the latest version of PdaNet+, even if hotspot mode is disabled.
The latest versions require the app to be put on both the client and server device. It creates a VPN between the two devices, via WiFi Direct, and is able to bypass tethering restrictions in most phones.
I've used PdaNet+ for many years and think it's a great app.
My experience with a BLU Dual SIM phone is that it'd allow hotspot. And with a DUAL SIM phone, you can switch phones via menu and not have to physically swap SIMs.
I have the same experience as PEW.
I wonder though if single SIM BLU phones also allow native hotspot without carrier subscription.
"If you have a AT& T hotspot how much data can you get for it?"
My answer is as much as you can negotiate! I have more than 700MB on mine. 