My fiancé owns a corporation and we want to become partners for a separate business using a DBA under this entity? Is this possible?

I'm not sure I understand your question, because you write about a corporation and a sole proprietorship, which are two different things.  By definition a corporation is not a sole proprietorship and a sole proprietorship is not a corporation.  If you mean to ask whether a corporation can buy a business which was operated as a sole proprietorship, the answer is yes.  For example, the corporation can agree to sell a 50% interest in the corporation to the owner of the sole proprietorship in eschange for all the assets of the business. If you and your fiance agree, you can become a co-owner of the corporation and operate a different business under that corporate name, or under a d/b/a owned by the corporation.  You can then agree on your respective employment compensation, profit sharing, management responsibilities and rights, etc.  I'm not sure you understand all the implications, however, including tax implications, and I think you should probably consult a Florida corporate attorney.