Ok, so I'm the naive overenthusiastic whippersnapper here...
I'm approaching mid thirties physically if not mentally. I have wanted to do woodworking most of my life but it's not been possible for various reasons. As such I'm a novice, self taught and had to buy all my tools, generally limited in budget. I'm also relatively time and space limited. It is still possible and I have built some of my own hives from cedar.
In terms of cost and quality, yes, seconds are probably a more consistently safe bet. However, it is possible to make them yourself for less. I tend to make a bulk number of a certain part at a time.
If you have the tools and the experience it should be a doddle for you. If you can find a local source of cedar and make a decent number then it's ok. For one or two it's probably not worth it financially. It's also a question of how complicated you want to make it as you can adjust aspects of the design to make Nationals boxes simpler, such as the handles.
Pallets provides a free source of wood- sometimes planks are wide enough for shallows, for deeps and with the bits not wide enough, you will need to join them. Factor in the time deconstructing them though.
In terms of tools, my first hive and nuc boxes were done with a borrowed circular saw, a wood saw (using this to measure angles too), tape measure and palm router with basic table jig. In my view it is possible to use just a tape mesure, wood saw and pencil (plus hammer nails and glue for assembly!) if you simply the design and take your time. I now have a basic table saw and second hand mitre saw. Whilst I need to build some better jigs to make things faster and more precise/consistent, along with the router these are sufficient for my purposes and available space. Ultimately it will come down to how much time you have, how you value your time, how quick you are and if building your own kit carries inherent value to you (it's not just about the monetary perspective).
As for comments about time it takes and being time poor... each day we have the same number of hours as everyone else, it's how you use them (hence time limited in my case). I could work 'full time' to earn as much as I can but I am fortunate in that I can earn 'enough' to get by without. It means things are often tighter than I'd like but it's a case of what you value. I do things this way because it means I have slightly more time for my family and things I love doing now. You never know how long you'll live and they say not many people get to the end of their lives and wish they had worked more. If doing something brings you joy, do/pursue it.
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