How long will it take to get a work permit if I marry a US citizen?
If you marry a USC and apply to adjust your status (assuming your eligible) you will get a work permit within 90 days. Consider hiring an immigration lawyer to review you case before you apply to adjust your status.
If you are in the US and marry a US citizen, you will want to file the I-130 concurrently with the I-485, work permit request and advance parole request. By filing all these together, if you qualify to do so, you will avoid having to pay the additional filing fees for the work permit and travel document. Processing times vary on all these documents, but I have seen the work permits being issued as fast as 30 days, and in a number of recently filed cases the interview is taking place within a couple weeks from the time the work permits and travel documents are being issued. Of course each case is different and timelines change based on the volume of applications USCIS receives.
This is general advice and may not be fully applicable to your situation as facts specific to your situation may affect the advice that should be followed. It is suggested that you retain a lawyer to aid you in this process. This advice does not create an attorney-client relationship.
Speak to a lawyer about your options.
If we assume that you are eligible to apply in the U.s. for a green card based on your marriage to a citizen, you can apply along with the main green card petition for an Employment Authorization Document. This normally comes through about three months after the filing (though the whole green card process will probably only take about five months).