Filing for form I-130

Your filing form I-130 for your soon-to-be husband who is here on the visa waiver program does not excuse his obligation to return to his home country within the 90 days. He is only allowed to remain in a quasi-legal status if you also file form I-485 adjustment of status application to permanent residence. Then he could remain in the country until both he and you are interviewed in connection with the applications.  I note that if you were engaged prior to his coming to the States, there could be a question of whether he misrepresented his true intentions when he entered under the visa waiver. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.

If you marry while your fiance is here, you should file both the I-130 and the I-485 together.  That way your spouse can remain in the US until the green card is issued.