I originally found my Grey online, but later found her at a parrot shop where rescues/rehomes are sold. Her age is approximately 5 to 8 years of age. She is past the sexual maturity/terrible twos phase, which is nice.
My recommendation is to continue to visit the Grey(s) you're interested in and see if you "click" with any of them. It took a few weeks of visiting my Grey at the shop to really bond with her, and become friends. At first she was shy and wouldn't let me handle her... but becoming a familiar presence that spent time playing with her (and giving her juice!) made all the difference, and I became one of the very few she'd step-up for and handle. The clerks noticed this change with her, and I had to adopt

One of the things the Avian vet told me is that unfortunately, a lot of Greys don't make it past 30 years of age. This could be because of insufficient diet/lack of flight.
I will say that owning a Grey is an experience like no other... it is like living with a feathered toddler, complete with vocabulary (well, if the Grey talks, as not all do). Greys are incredibly intelligent but they can be really demanding (well, at least my Grey is... she is like a drill sergeant sometimes when she wants her way). They are also dusty so you'll need an air purifier.
Also, my Grey prefers me but she also likes my partner and lets him handle her, as well - a first, as she was known to hate men. All Greys are different but she had some good socialization while at the pet shop. She prefers me probably because I feed her and spend the most time with her - but this is speculation. Before I adopted her it was said she was a "girl's parrot" as she preferred female humans. Greys are known to gender discriminate but, again, this isn't always so as she likes my partner.
The male Grey that I really liked, though, did not like men whatsoever as he wanted all the ladies to himself.

So, it really just depends on the bird...