Do not take this to mean any certain company is this way but can tell you two who have done this, Dell Computers and Sears.
It may be ZERO for X time but then you get hit with back interest at very high rate if you run the full period of the loan. Not being late, not missing a payment. So less say it have ZERO rate or NO PAYMENTS due for a certain period of time. Well say that interest rate is low for 36 months but they will break up the payments into 48. So you are billed for a payment on a 48 month period and do not realize what is going on. At the end of 36 months wham...since it is not totally paid for back interest now hits the loan.
Again, I know for fact Dell Computers and Sears has done this. Very dishonest to me. This is the reason some furniture chains can make hugh profits with NO Payments for say 6 months.
But there is still a cost to Zero interest, notice they are now being little more honest (car companies) with zero interest or few thousand in rebate.