Yes, this is a trustworthy site to work on and earn money answering questions online. This site has a higher pay rate for answering questions than a few other questions and answer sites. You can earn a decent amount of money working on this site. All you basically need to do is answer 10 question to earn $1 from the site. That means that you'll need to participate on this site and answer around 300 questions to earn the $30. However, if people continue to thank you for your answers, the money will add up quicker in your account.
Anyone who asks questions on the site and comes back to read their answers should remember to thank a person for their answer they have given. This will help them earn money on the site and they will remember you and thank you when they see you answering questions on the site. You can add a thank you for any question on the site and it doesn't need to be your own. This is a good practice to help out the other members on the site and in return, they will help you out.