At least 2 years, unless the green card holder naturalizes and then elevates his/her petition on your behalf to spouse of a citizen. You will the get a work permit within 2-3 months and a green card within 4-5 months total, from the time of the "elevation".
Behar Intl. Counsel 619.234.5962 Kindly be advised that the answer above is only general in nature cannot be construed as legal advice, given that not enough facts are known. It is your responsibility to retain a lawyer to analyze the facts specific to your particular situation in order to give you specific advice. Specific answers will require cognizance of all pertinent facts about your case. Any answers offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship.
Spouses of legal permanent residents are currently waiting a bit more than 2 years after their partner files an immigration petition before they can go forward with getting a green card. See: http://travel.state.gov/visa/bulletin/bulletin_5834.html
However, there are a number of things that could make getting a green card a more lengthy and difficult process. For example, if you entered the USA without permission and then stayed here more than 6 months without having any immigration status, you may need to return to your home country and stay there for 3 years or even 10 years before you can get a green card.
Call a lawyer for a consultation. There are a number of questions a lawyer would need to ask you before they could give you advise that is tailored to your specific situation.