I don't think there's one right path here, ADeadlierSnake, as people come into diving (and later tech diving) at different ages and different periods in their life. In addition, small details like which agency you start with, which agency you decide to do tech training with, where you live, and who your buddies are will all have an impact on the amount of money you are likely to spend to get into this niche.
As someone who started diving five years ago and am now 32, I can mention some trends I've noticed that may help you get to where you want to go:
1. I was horrible at saving money up until my late 20s and so was essentially "starting from scratch" when I began diving, but fortunately this coincided with a new, high-paying job at the time and I was still single (unlike my current situation with a wife and two kids). It's true that most people spend most of what they make anyway, and this is even more true for people fresh out of school who will likely take the next ten years to figure themselves out and decide on what hobbies (and the friends that come with those hobbies) to pursue. As such, it may just be a matter of getting better and better paying jobs over time coupled with your ability to "settle" on diving as your "One True Hobby" (i.e., the one that will receive the most of your money).
2. When you finish college, move to a place that's on the ocean and, preferrably, with WARM water. This will save you money by not requiring you to purchase the more expensive items like drysuits (vs. wetsuits), steel tanks (vs. AL tanks), that colder water diving requires, but it also means a massive reduction in travel expenses to/from your favorite dive sites. This means more dives per day when you do go out and, thus, more diving experience in general. I know many people who are dedicated enough to drive 2+ hours to do dives every weekend, but if you could be a mere 10-30 minutes away from all the local sites, why shoot yourself in the foot and live farther away? Save the home up in the mountains for later in life once you're more settled.
3. Do
not invest in equipment until you have sat through a Primer or two of the agencies that have caught your eye and are in a better position to make a decision as to what to buy. As I started with PADI and bought all of my equipment that my teacher recommended while I worked through the PADI certification ranks, ultimately I had to sell it all when I joined GUE. I was fortunate that I had a friend just starting out who bought all of my "old" equipment off of me, but if I'd had less of a job, I would have been out of the water for quite some time to recoup those losses.
4. With all above the above settled, you can actually get by
relatively cheaply on technical diving. In my case, I started with:
a. Two first stages, two second stages, one SPG, all necessary hoses (you can start out converting your regs from doubles's setup to singe's if you want to dive with your single tanks on a particular weekend).
b. Two masks
c. A 3ft SMB w/ spool
d. A 40# (doubles) wing (you may also wish to have a 30# (singles) wing for single tank diving). But, both can use the same 6lb stainless steel backplate.
e. A wrist mounted compass, wet notes, and a cheap bottom timer (not a dive computer)
f. Fins of the non-split variety.
g. One set of AL80 double tanks (with SS bands and manifold). You may also have one or two single AL80 tanks if you think you will be doing that type of diving with friends.
h. One or two 3 C-cell backup lights
i. A primary light. (10 watts or greater, though you'll eventually want an 18 watt or 21 watt, so it may be cheaper to get one of those second-hand right from the start)
Again, assuming you went with an agency like GUE, you don't actually need some of the more expensive items on that list to start with their Fundamentals training. And here, I'm thinking about the doubles, doubles regs, backup lights, primary lights, 40# wing, since you can take courses like that in a singles setup. However, since you know you want to go further into technical training, keep in mind that you'll be purchasing them anyway at some point.
Then, one of the more expensive aspects will likely be your training. But (at least with GUE) there are experience requirements between courses (25+ dives at that level), so usually you have enough time after you finish one course to save up for the next.
The more expensive items that we all drool over and that can be a serious money pit, but which do not impact the actual costs of technical diving implicitly are: dSLR cameras or HD video cameras, camera housings, still camera strobes, video camera lights, DPV(s), DPV camera mounts, drysuits and drysuit undergarments (though I'd argue that this should be your first purchase after the above mentioned items are taken care of), dive travel, extra bottles used for stage/deco gas, extra double tanks (for example, you might keep a set ready with trimix in them, but want to have another set or two with Nitrox for all the other weekends you're not doing a tech dive), extra "dedicated" regs to each type of bottle (deco/stage, doubles, singles, so you're not having to swap them out each weekend if you change your tank type), maintenance costs for all of these items on a yearly basis, courses that teach you how to maintain your own gear (tank inspections, reg repair, etc.), gas boosters (if you decide you want to "save a few bucks" by filling your own tanks, etc.
As usual, your mileage may vary.
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