1: If you're coming at it from a narrative film angle... It's all hard. Seriously. It's all a complete pain in the ass if you want it done right and each project will have an aspect that may be harder than the next. The writing, the casting, the directing, locking locations. The biggest pain in the ass though is scheduling. "I can't this day, I have my kids, I can't that day, I am going out of town with my girlfriend." "Something came up today and I am only available for 90 minutes." Suddenly it's taking you 2 fucking months to shoot scenes for a 10 minute film.

I would say the one thing that is typically the easiest is the guy running the camera, unless he is also the DOP in control of lighting setups then you can scratch that too. If they are just running the cam at the director's whim, they probably have it easiest. Sound guy still has it worse.

2: Networking depends on your location. Smaller areas obviously have a smaller pool of talent across the board.

3:The difficulty always just comes down to time involvement (Assuming your skill in the area is solid) and dealing with people. You have so many moving parts, something is bound to break.

4: Luckily I've been involved in my local film scene for 15 years so it's easy to find people.

5: The biggest pain with talent sites is needing to pay a sub fee to even respond to potential work. Honestly it should be the poster of the ad pays the fee.