Learn what a letter of agreement is and how to write one, including a template and example to help you get started crafting your own. Stepbystep guide on how to write contracts for leases, business partnerships, and employment contracts.A letter agreement is a written legal document that is made between two parties who want a simple way to make their discussions of a transaction official. A Letter of Intent is a written document that serves as an initial agreement between two parties concerning the terms of a possible purchase or transaction. This Settlement Agreement and Mutual Release (the "Agreement") is entered into on this. Think of it as a detailed conversation in writing where you lay out exactly what each person or business will do, when, and how. A Letter of Agreement is a document that outlines the terms and conditions of an agreement between two parties, like a more concise version of a contract. The easiest way to edit Agreement between Parties Living Together but Remaining Unmarried with Regard to Sale of Residence - Illinois in PDF format online. Once all parties sign a letter of agreement, it becomes a binding legal document. Amount of Agreement.