Letter of invitation to visit USA?

Question

hi guys i want to write a letter of invitation for a friend, i know what should be written in the letter and send it to the friend, my question is

should the letter get notrised by any public or just write it and send it to the friend ?

Answer 1

letter of invitation to visit U s A from nigeria

Answer 2

i want to  know how to write a letter of invitation to Nigeria from U.S and what document did i need to attach to it when sending it to the person

Answer 3

want to be freinds

Answer 4

i want my friend in the usa to send me an invitation letter through e-mail,i dont know if it will be ok?