Using iphone with tmobile plans/flex pay

[helloallison]

I was thinking of switching all 3 of my family's iphones, unlocked, to T-mobile's Even More Plus (no annual contract plan) but I heard they do a credit check even though it's no contract? so there was another option where they don't do a credit check and it's T-mobile's Flexpay. I was wondering what the family payment plan for that was, is it the same as the Even More plus payment plans? and how much would the data plan for 3 phones cost? I heard it was $25 for each phone, which would be an additional $75 to the bill? Is there an activation fee for Flexpay? I have bad credit so, this would be the only option I can do to be able to use the iphone.