Which used Nikon DSLR under $500? Currently have a 35mm/f1.8 prime lens

• Budget: Under $500 USD
• Country: US
• Condition: Used
• Type of Camera: DSLR (but open to Mirrorless, if appropriate. Looking at Sony A6000)
• Intended use: Photography (minimal Post processing, possibly none)
• If photography; what style: Baby photos
• If video what style: Rare, but occasional baby videos
• What features do you absolutely need: Nothing, just needs to take sharp/crisp photos
• Portability: Anything is okay
• Cameras you're considering: Nikon D5600, Nikon D7100
• Cameras you already have: Nikon D3000. It doesn't take the sharpest photos, color is yellow/warm in indoor settings. ISO performance and low light performance is just weak.
• Notes: I'm very new to photography, but have had the D3000 for 15 years or so. Just looking to take crisp photos of my newborn.

UPDATED: Thank you all so much. I ordered a D7100 used from KEH.com for $300. Will be looking at a speedlight as well!