Working Holiday Help Me

help please am ready to go and submit my working holiday maker visa any moment from now all my documents are ready but one issue is bordering me. in the whole form their is no place they ask for any letter of invitation or i should write where i will stay.but i met someone whom says i need to get a Uk host before i can get the visa. is this correct because even in the checklist at the back of the form their is no place that they asked for any UK host documents.this is why i choosed the visa because my friend in london do not want ot give me any invitation letter.he is conservative. i need advice from people who are on working holiday maker visa or who know much about the visa. lest i forget can i use a mortgage bank statement. i bank with a mortgage bank.what is the minimum money that need to be inside my account for this type of visa.