I checked out that link, what I saw was the following:
1 line plan:
Unlimited Enhanced for $90/Mo <==|
Unlimited Plus for $80/Mo <=====|___These two options are what I PRESUME you would have to sign up for FIRST, then you will have the following available if you want:
Additional devices:
Tablets**, Cameras & Connected Cars:
$20/Mo <====|--- Alright, what I see here is what COULD be the ACTUAL business opportunity. You buy many of these $20 (once again "DATA Only SIMS for supposed TABETS, CAMERAS AND CONNECTED CARS" and then you give it to people to use for either their smart phones (working as Data Only) or an actual hotspot for $350/yr. Your yearly investment would be: $20 12 =
$240 and then your customer's sale at $350 - $240 (your investment in 12 months) = $110 earned in a year.
THIS does NOT include any taxes and fees that AT&T would in no doubt charge you, so to cover yourself for these taxes and fees you might not want to sell these $20/Mo data only sims for $350 a year, you might want to sell them for $400 to $450 a year.
and........
Remember that line I talked about in the first section? You will need to get that first before you can get anything else, that will turn into an overhead investment, that $90 that you will have to pay every month (once again, plus taxes and fees) will add up to $90 12 = $1,080 a year before ANY taxes and fees, expect to be paying about $110 a month when AT&T includes all taxes and fees, if that's so, then your final yearly bill would be: $110 12 = $1,320 and lets say AT&T charges you $30 every month for the additional $20/Mo data only SIM plan, that data only SIM plan final bill would be: $30 12 = $360, just adding $10 more to that $20 monthly bill all of a sudden rose your overhead from $240/yr into $360/yr no longer making it viable to sell it to $350 a year to your customer hence why I would recomend a price of $450 a year in order to still turn a profit after paying all those taxes and fees.
If you get ONE data SIM ($20/Mo + $10 in Taxes and Fees/Mo) and ONE Line1 ($90/Mo + $20 in Taxes and Fees/Mo) plan you would end up paying a grand total of $1,680 in one year (OUCH!!) and even if you managed to sell one "AT&T Unlimited Data Plan" for $450 a year it would only lower your overhead down to $1,230 In order to break even you will need to be able to sell at least 4 SIM cards which will give you a gross earnings of: $1,800 completely wiping off that huge yearly bill of yours of $1,680 and earning you a NET profit of: $120 (not bad), your profit will now start getting much better after doing the 5th sell and more.
My conclusion:
IF you are REALLY sure that you are going to be able to get A LOT of customers within the year, then I would say: go ahead and I will wish you good luck
Complications:
Any illegal things your customers do under these SIM cards you will be responsible for as the account is under your name and address and of course you can tell the cops that "plan" was sold to a customer of yours (so have your Terms of Service and your Privacy Policy ready for your customer to sign so that your customer won't sue you for providing the cops the customer's information) but you would still have to deal with the headache of the cops knocking at your doors every time something happens.