This affidavit documents the cohabitation of two individuals for over ten years without being legally married. Use our I130 affidavit sample and tips to create a strong affidavit for your spouse.Include these key points and avoid common mistakes. This affidavit documents the cohabitation of a couple for over six years without being legally married. Step 1 – Specify whether one or both spouses will be completing and signing it. Step 1 – Fill in the information of both parties. The first step in writing a cohabitation agreement is filling in the parties' information. .Two individuals seeking to become domestic partners must complete and file a declaration of domestic partnership in person with the City Clerk Department. Next, include the details of all the parties involved in the document. As the affiant, you'll need to include your name and contact details.