I'd say that's a good deal, but I would ask the lady (and yourself) a few questions.
Why is she rehoming him?
How tame is he? Will he go to strangers, or at least tolerate them? Can he perch on your finger? What kind of attention is he used to getting?
What was he fed (this will give you a good idea about how much she tried to care for him to begin with)?
Have you owned a parrot before? What do you plan on feeding him? Do you know how to handle a bird that may not have been treated well in the past and already has bad habits? If not, I would not suggest a Sun as a first bird. They are bossy, independent, destructive, noisy, difficult keep from being "one person" birds, tend to get aggressive if they don't get their own way, and messy. Suns are VERY loud. I have to repeat that. I have had more than one in the past. I love them, but now I have two Dusky conures instead, and they are much easier to care for and train. If you've never had a bird before, Suns will not give you a good impression. On the good side, they are clowns, can be very affectionate (with their selected person, and this person may not end up being you in the end), smart, and are absolutely beautiful.
There's just so many questions I'd have for your and the previous owner before I gave you my opinion... I hope you make the right decision!