Short answer: Less than 22 days.
Long answer: Customers are allowed 14 full days within which to review your work. If they don't manually review it, then it will be auto-approved on the 16th calendar day, counting the day you submit your work and the day it is approved. When your gig is approved, it disappears from the "gigs in review" section of the Gigwalk app.
Your payment is automatically sent via PayPal after the Customer approves your work. Paypal's processing time is usually less than 2 days, but may take up to 7 days.
Example: You submit a gig sometime on the 6th. If the client hasn't reviewed your work by the end of the day on the 20th, then your work will automatically be approved on the 21st. Then, Paypal will begin their processing, and you will be paid by the 28th.
If this is your first time receiving a payment from Gigwalk, please also see this FAQ: Setting up & verifying your PayPal account.