concerning payments, I prefer an advance, but in the end is how the customer decide. hosting and domains are paid up front, if a web development requere. passwords and users are given to customer after confirming full payment.
the form of communication that be appropriate, can be for email, Skype, Viber or some other means to be good between both parties. a convenir, to start allways by emal. i belive that the customer has the last word