Help Please

Hello and good morning from sunny London.
I have been fortunate enough to be offered a job in Baku starting in July which i have accepted so i am looking forward to an exiting new chapter in my life.The problem i have is my fiance.I need advice which is the best way for her to be able to stay with me obviously permanently.I am reading that she needs an invitation letter is this correct from an Azerbaijani person?She will be coming out after me as her passport needs re newing but we can accept that but i am very afraid that she wont be coming long term.She has no job at present but will look if nessercary when she gets there but to be honest she doesnt have to work.Please can anyone help with advice.My e mail for private messages is [email protected] Thank You