According to the examples, this voicemail greeting is primarily used to interact with individuals who do not know who Mike Avery is or what he does. The second example displays a higher level of professionalism by clearly identifying who Mike Avery is, and what his relationship to the caller is.
8. We could be in, we could be out. You could leave us a message and later find out.

Consider for a moment how your phone is currently being answered. Professional courtesy is quite often not the standard for many college students. An abrupt "Yeah!" could be listed among the more courteous greetings. The more outrageous remarks will often buy you a major black mark in the professionalism category—even if it was your roommate answering your phone and acting crazy. A simple "This is ____" is always a pleasant change for a college student call. Make the change today, before the next (or first) employer phone call. If you have a landline, you should also encourage your roommate to do the same.
8. “Thanks for calling [your name] at [your company]. I didn’t mean to send you to voicemail but I am either on the line with another client or on the go. Leave your name, number, the reason for your call today and the best time to call you back. I’ll speak with you shortly! ” Your caller probably wanted to reach you, not your voicemail. Advise your caller that you’re simply on the line with another caller and you’ll be right with them.