Although not a requirement, your U.S. host can write a letter. We've provided a sample invitation letter for a B-2 visitor visa.The letter should include specific details like your relationship with the visitor, the purpose of their visit, duration of stay, and financial arrangements. I would like to invite you to the United States of America to stay with us for three months. It would be very nice to have you with us. I would like to invite both of you to the United States of America to stay with me for 6 months from March 1, 2010 to August 1, 2010. What should the letter say? Use an appropriate tone.