How do I apply for a K1 visa and bring my fiancé to the USA to pursue legal permanent residence and citizenship?

You should understand that once the K-1 visa is approved and your fiancé comes to the US, you are given 90 days to marry. Therefore your statement that you "intend to marry someday" is not appropriate. Other than that, you would have to show U.S.C.I.S. proof of your bona fide relationship and having met within the past two years when filing the I-129F form. The question of a cosponsor may come up at the time that he is interviewed at the American consulate or embassy and the co-sponsor should provide the I-134 affidavit of support with job letter, banking statements, proof of recent pay, and at least the last year's tax return.  Once your fiance enters the U.S., and you are both married, he can file for an adjustment of status to permanent residence on form I-485 and at the same time request work authorization on form I-765. 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.