If B2 visa married US citizen, how long does it take to get green card, can I continue stay when my visa expired?

Generally, a foreign national who enters the U.S. lawfully and with inspection, such as with a B2 visa, and then becomes married to a U.S. citizen, may apply to adjust status to become a Lawful Permanent Resident (to get a "Green Card"), and the fact that the foreign national may have overstayed her visa will not stand in the way of eligibility. Upon filing an adjustment of status application with application for an Employment Authorization Document ("EAD" or "work permit"), the foreign national may expect to receive the EAD in 60-90 days and thereby become authorized for employment while the case is pending. The USCIS is inconsistent in the amount of time it takes to process a marriage-based adjustment of status case, but generally a couple with a well prepared and fully documented application will be scheduled for an interview in about 3.5 - 4.5 months, and approval should take place at time of interview. Some immigration law firms, including mine, offer legal services on a "flat fee" basis so that a client will know the total expense from the very beginning, and a few immigration law firms, including mine, offer an initial consultation free of charge. An initial consultation is needed to learn all of the relevant information about the couple and to determine the exact steps that will be necessary to take once that is determined, a "flat fee" can be determined.