A letter in support of a visa application should be addressed to the consulate or embassy in the potential visitor's country, stating the supporter's relationship to the applicant and the reason for the visit, as explained by USA Today. A letter of support can be written for anyone, but the more loose the relationship, the more important it is to justify the visit, as stated on immihelp.com.
The letter should include the full legal name, contact information, mailing address and physical address of both the visa applicant and the person writing the letter, according to USA Today. It should state the citizenship status and date of birth of the person writing in support of the visa and include a copy of a passport or birth certificate to prove citizenship. The letter should also include information such as where the visa applicant will be staying and how they will be supported while in the country. It should include proof of employment and income of the person writing the letter as well as recent bank statements. According to immihelp.com, a completed form I-134, or Affidavit of Support, should also be included with the letter. Immihelp.com recommends sending the letter and supporting documents directly to the person applying for the visa. The letter and supporting documents should be as recent as possible and no more than six months old.