You can pay via Interac eTransfer (recommended for clients with a bank account in Canada) or Paypal / credit card (fees might apply).
Small projects are paid in advance. For bigger projects, I send an invoice for the first half and payment of that first half is considered as the “go ahead.” Once I finish the document and send it back, the second half of the payment is due. For long-term projects, it is possible to arrange for payment in installments.
Established clients are issued an invoice at the end of the month for the work done that month.