Used 2010 Prius 2

I'm looking at buying a used 2010 Prius with 124k miles on it. The dealer is letting me drive it around for a few days. Asking $7k for it. KBB estimates $7.3k - $9.4k for fair market range. So it seems odd to list it low. It does have some damage to the rear passenger door though, but besides the window it seems to be minor (I don't care about looks).

I am new to driving a Prius so I just have a couple questions.

When I drive, the gas starts up usually pretty fast, like at 10mph or so sometimes less. I tried various accelerations and it didn't seem to matter. I thought it was supposed to stay electric up to 20-25mph before kicking in. Is that normal? How can I tell if the battery is healthy?

I planned on having a mechanic do a thorough inspection. Would a Toyota dealership be the best place for this?

Thank you!