I'm Confused & Need Advice!

Sorry if I’m posting on a wrong thread, its my first day and need some work to find out how to navigate, but this question is kinda tricky…:blush:
I’m a US Citizen I’ve applied for my wife and two children (3) whose visa is expected to be approved (fingers crossed) shortly. Can I file I-864 before we receive the approval letter from the NVC?
Also, do I have be employed at the time when I file I-864, or I could be unemployed and still could file with $120 fee? My annual income is about 42K and I’m applying for 3 immigrants.
When replying, please provide some reference.
and, thank you all for helping me out, in advance!

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