Affidavit of Support

Im trying to figure out the household size of a sponsor. Ive watched many videos on it but I just want to make sure I am doing this right.

My mom is petitioning me. She is single and has no dependents all her children are over 21 years old.

Mind you I still live with her... Included in her household would be her (the petitioner)
and me (the beneficiary)
For immigration purposes her household size would be TWO right?

Does it matter that my half brother and his girlfriend and their daughter live in the same household?

Tax household size. Unless your mom claims your brother and his family on her taxes the answer is 2.

Thank you. She does not claim anyone in her taxes

Does anyone know when you file petition I-485 do they charge extra (aside for payin for I-485) for applying for the Employment Authorization Card?

No, I-765 and I-131, initial and renewals are free if you paid the fee for I-485.

If you get a fee waiver for I-485 you need to either pay or get another fee waiver for renewals.

Thanks. How long is the work permit good for? Is it good until the I-485 is approved and I (hopefully) get the green card in the mail?

2 years, renewals are free, it also comes with an automatic 180 day extension if you file for renewal while the previous one is still valid.