If I can get a good deal I shouldn't have a problem finding people to join. I have an inside discount code but I wouldn't consider that a great price even with 8 lines
9 lines with insider and some of them free starts to get good. It also depends on the rate plan you go for, MagentaMax is a significant premium over Essentials, so it depends what you’re looking for.
Lastly, if you owe on devices with your current carrier, T-mobile will pay off up to $1000/line with keep-and-switch (also known as BreakFree and CarrierFreedom), subject to some fine print terms