Indoor rabbit cages are great because they have a top door for ease of cleaning, and a side door for interacting with the chicks without scaring them by reaching down from above. I wrap a sheet around 3 sides while they are tiny to block any drafts.
With broody chicks I found that I can take them out as early as day 1, while brooder chicks need up to 3 weeks to grow enough feathers to stay outside in late spring/summer/early fall weather.
