If a person A posts a task, then task doers will bid to have that task assigned to them. Person A will select a person among them (person B). Once the task is completed, person A will pay the amount agreed and my website will process the payment, taking a fee out of it (hence ecommerce somehow).
Do you think I would need Multisite to have the tasks listed on one side, and the pool of people willing to do them and listing their skills in other?