I just interviewed there a few days ago. I'm a 31 year old jet FO with around 2700+ hours and 0 PIC turbine. My group had people aged from 24 to 51. Most of them were in their early 30s to early 40s. Most of the others interviewees had from 4000+ to 8000 flight hours and a lot of PIC turbine time.
I think the person with the second least amount of hours next to me was a 38 year old guy who is retiring after 20 years of military service, had over 4000+ TT, 1400 turbine PIC, and has been flying Gulfstreams worldwide for the military. I felt a little underqualified, but I gave it my best.
I don't think NetJets has a specific age requirement, but since they operate part 135 and part 91K, they are required by the FAA to type rate all their pilots in the airplane, even the FO's and thus require an ATP certificate.