1. The Shed itself - any recommendations? What materials are best?
You can
build your shed easy or you can
buy a pre built shedIts really not worth build that shed from Fire-resistant Building Materials
2. Electric - Can I just hire an electrician for this? How much cost am I looking at here to get this set up, potentially?
You definitely need to hire a electrician for this job, you might need to upgrade you home service max amperage, or install second service point, its really depend on what is the max amp you are planning to use in that shed. After the main breaker panel in the shed is connected to the power gird ( power meter) , you can pull your wiring easy inside the shed, if you know some basic calculation about amps/voltage , how to install breakers into the panel
3. Ventilation - This is the part that gets me nervous. I understand the basic concepts here, but when I start thinking about exactly how I would go about doing this, my head spins. Could I do any of this myself? What kinds of intake/outtake fans should I use? What about when it rains or snows? etc etc. The more help and hand-holding in this area, the better.
Air circulation is very important, dont even think to use AC units to cooling your rigs ... You probably really dont need fan to push air into the shed , but you need a
high cfm industrial fan to pull the warm air out... You should use
some kind of air filter ( merv 6 or merv 8 ) in the shed opening, where the fresh air sucked in, keep the dust, pollens out
4. Security issues - it would be in fenced-in backyard, lockable and I could hopefully put a door sensor from my home security system on there. What kind of fire protection would I want here, ideally? Is there anything I'm not thinking of?
as a fire protection... use the right sized breakers, dont overload your wall plugs, keep the 80% rules when designing your wiring... If you insert a 30 amp circuit breaker to the panel, make sure you are not overloading that circuit .... so use around 24 AMP on a 30 amp circuit breaker
Use metal shelving in the shed, use metal frame for your rigs
What other issues am I not thinking of? I want to keep this as simple as possible.
Use
switched pdu's with remote access, so this way you can hard reboot your rigs , use
switched, metered pdu's if you want to see the power usage for each rig you are using
Dont use 110-120 Volts ... use 200-240 volts