I have flexible working hours but please do undertand i am in +5:30hr GMT (IST) timezone. I work on a regular job from 9:00am to 7:00pm. Monday to saturday. Primary contact which i prefer is email, you are facing any problems you can always email me. If something is urgent you may use Viber, Whatsapp or Gtalk to get in touch with me.
Regarding payments i usually dont ask for advance i first evaluate the work to make sure i can handle it, then i will give a final proposal to the customer.
There will be deliverable and payments need to be released when the deliverable have been met, checked and accepted.