We want to be sure people are compensated fairly for work.
Upwork does not support contract rates under $3.00 USD per hour for hourly contracts. For fixed-price contracts, the minimum pay for a project is $5.00 USD, unless the client requires you to work a certain number of hours on the project. In that case, the client must pay you the equivalent hourly rate of $3.00 per hour.
For example, a client posts a fixed-price job asking for someone to spend 10 hours reviewing their website. Since the client is asking for a set number of hours to be worked, they would have to follow the rules for hourly contracts and pay at least $3.00 USD for each hour, totalling a minimum of $30.00 USD for the project.