There is no good answer to that. The problem is, what equipment are you going to use? Brand A may be widely available, and widely discounted; Brand B may be manufactured in small lots, available only directly from the manufacturer, and require a mortage on your house! Until you take your course, learn about and decide on which equipment you will need, you really shouldn’t be spending a lot of money up front. The exception to that guideline is, if you have a dive buddy who is a cave diver and he/she wants you to dive with the same gear and configuration as them, then your problem is easier (but it’s still a problem). This isn’t necessarily the best approach, but there is some validity in having the same “kit” as your primary dive buddy. But if your dive buddy is sloppy, or made the wrong decisions, had a less-than-enlightened instructor, then you’re making the wrong decision, too. Maybe you should get another dive buddy! The other issue is: cave diving equipment IS expensive. There is no way around that! Even at wholesale prices (which you are unlikely to get), you could spend $4000 putting together a kit, the double tanks, the manifold, the backplate and harness, wings, dual regulators, SPG, knife, primary and backup lights, etc., etc. All your equipment should be of the highest quality since you are betting your life on it. But that is the real point here: if you have a problem with your gear 1000-feet back into a cave, you aren’t going to be able to dig a hole through the limestone to surface: you have to deal with it. Given that situation, do you REALLY want to go cave diving with less than the best regulators, etc.? I didn’t think so… The redundancy required by cave diving means that your kit will be almost twice what an open water diver would spend. So, in summary: it will be expensive, but ask around and you might find good sources.