Generally speaking I think it is not a wise idea buying an adult from someone other than a well known breeder and even that may be questionable.
All depends on your budget. You will likely pay twice as much for an adult Mojave than a Pin. You could buy a 0.1 Pin and a 0.1 Mojave in the 700g- 800g range for close to the same as a breeder Mojave girl and have both up to size with no problem by fall.