How much debt am I in because of photography? None whatsoever.
How much debt have I been in because of photography? I hate to think, my debts got pretty high at one point, but photography was only a part of it.
Having been there, but paid it all off now, I can say that the consensus above about "don't do it" is probably good advice, particularly if you tend to keep acquiring stuff.
However, there are times it makes sense. I bought my 300 f/2.8L on credit, it was from a store which offered interest free "buy now, pay in 12 months" credit on all large purchases. I didn't have the money to hand but figured I could come up with it in 12 months time. Of course, that was the critical point, as the deal comes with an option at that point of pay it off in full, no interest charged, or pay it off over 36 months. The catch being that they hope you can't pay it and spread it over the 36 months as the interest is then horrendous and backdated to the purchase date 12 months previously. Take that option and you will end up paying over double the original price. However, I never intended to take option 2 (yeah, I know, nobody ever does) my plan, if I didn't have the money, was to simply sell the lens and top up the money that raised to pay the bill. Sure, I would probably lose £500 or so when I sold it, but it would cost that much to rent one for a month, so I was happy to do that as a years "rental" if it came down to that. Fortunately, it didn't, I had the money available when the due date came and made sure I got it paid off just before the 12 months were up. I have now had the lens for about 6 years and still love it, I am crap at saving as I always end up spending the money on something else, so I probably would never have got the lens that way.
So, in that case, using credit was a big plus. I got the lens I lusted after 12 months sooner than would have been possible and paid no extra for it (actually I paid less, as the price had gone up by the time I paid it off).
I suspect that the OP has a similar situation (kind of) with the 6 months interest free on his card. If you are fairly sure that you can pay it off in 6 months, why not go for it, it won't cost anything in interest. Just bear in mind that if you don't pay it off then it will start costing you interest. Of course, that may only be on a small part of the cost and just for a month or two.
I would go for it, get the lens and enjoy it for the next 6 months and get shots that I would miss if I was still saving for it. Just don't let the debt still all be on your card when the interest kicks in, and definitely don't buy anything else major until this one is paid off.
It is very tempting to allow debt to build, thinking that the repayments are still affordable and you are living within your means. But, it is very easy to end up paying large amounts of interest every month and find that, whilst you can still manage the monthly repayments without too much trouble, your actual debt isn't going down very quickly as so much of the payment goes on the interest. You could increase your payments each month, but that means putting most of your disposable income towards it and the sort of spendthrift personality that gets into that situation in the first place will have big issues having nothing to spend.
How bad did I let it get? About £35k (about US$:55k) at the peak, and there was no mortgage in there. All paid off now, thank goodness, and I would now only use credit when it makes sense.