Towards OPT you will pay the filing fee; whereas towards I-485/ I-765 the fee is a blanket fee. If you are filing an IR petition, I-765 towards I-485 filing may suffice. Best to discuss it with an experienced immigration attorney.
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Around six months.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.
Adjustment of status (that's what I-485 is) for spouse of USC (US citizen) tends to get adjudicated very quickly. Therefore, you may not need to apply for OPT. When you file I-485 application, you don't have to pay separate filing fee for I-765. Talk to an experienced immigration attorney near you.