The yellow tang is probably the most controversial fish readily available in the trade from what I've read and IMO
I've herd stories of yellows living for 15years with no issues in 55gl tanks and 250gl tanks but again this comes down to the fish itself and your commitment to your tank.
However, honestly IMO
the minimum size tank should be a standard 75gl tank for a while but you should upgrade when it gets to be considered med/large size.
But your safest bet of a problem free fish for life is in a 5' (but very wide) tank or a 6' tank
I would not tell you not to get it or that it won't be fat and happy, just dont be surprised or be ready to upgrade or trade for $$$ or credit.