Michael regarding humidifiers I have been using 2 humidifiers from Sears both with digital displays. Although the displays are not accurate in terms of the readings that they provide these units do operate automatically and are accurate to their own sensors. What I mean by this is that once you have a separate accurate hygrometer you can use it to calibrate what the humidifiers should be set at. For example in my shop, where the small humidifier lives, my hygrometers will read 45% which is what I want but in order to maintain that, automatically, I have to set the Sears unit to 60%. When it is above freezing outside (I am in Michigan) the humidifier is set to 55%. Always go by what the hygrometer reads in as much as the displays on the humidifiers are skewed by their proximity to the humidifier itself and the wetness in that area. My other humidifier is for my whole condo and lives in my living room where I have a wall of guitars in racks. Since I humidify my entire place the humidifier in the shop is really a back-up and rarely turns on.
In New York, as in Michigan, you will need to dehumidify as well in the summer. Dehumidifiers are a pain, noisy, you have to empty them unless you have a drain near by, and yet another expense. They also give off heat making your shop hotter in the summer.....
So my shop has a dehumidifier and an humidifier and with their help I can maintain around 45% RH year round. But I will tell you that I am sure sick of schlepping water to the humidifiers or from the dehumidifier......
There are many purists who will build most if not all of their guitars with mostly hand tools. This can be done and was the only way that it was done years ago. Even though I used my master bathroom that was not being used as a bathroom at the time I was able to get the following in there: Work bench, go-bar deck, 2 band saws, table top drill press, buffing arbor, compressor, thickness sander, tool chest, belt sander, and a shop-vac....... It was crowded but I liked it and it worked for me. Oh I forgot I also had a side bender in there too.....
There have been a lot of "show us your shop" threads here in the past so if you want to search the archives you may get some ideas.
As for what is required that is a wide open question because nearly every thing can be done with hand tools too. And you will get as many opinions to this question as there are members. Some things that will serve you well regardless of the school of building that you decide to subscribe to are a good #5 plane, a decent chisel (approx 1/2") and a way to sharpen them, and a band saw, a small one will work for now. My belt sander was of great help to me when I started out too and of course a good shop-vac too. With a drill press you can also thickness wood with a Wagner Power Planer. And you will need to either make or buy a side bending pipe or a bending machine. There certainly are many more but this is a good start.