The basic problem is that Furniture is marked up 3X the cost, while Cameras have a hair thin markup, about 7% for Canon. Camera stores may get rebates for meeting sales targets, but the profit still is low.
Camera stores generally depend on a percentage of customers buying items and accessories with a high markup. Without that, they could not stay in business.
I would only bite for one of the sucker deals that give X months with no interest when I had the cash in the bank drawing interest and earmarked for the purchase. The companies that finance those deals know that a high percentage of buyers will miss paying off the load before the due date, and suddenly, a whole years worth of interest is due at a very high interest rate.
Be very careful. I'd join a credit union and take out a loan, if I had to have one.