Airports can be convenient if you are flying into the city. However, they are also more expensive than other locations around town. Higher prices are because the airport itself charges a fee to the rental company.
Some of the best rates I have found are through Costco Travel. Costco has negotiated with the major car rental companies to have discounts on rentals. Costco membership is one of the most accessible group rates to be a part of because Costco membership has so many other benefits.
Turo is a gig economy app that lets people rent out their vehicles as a side hustle. Turo is kind of like Airbnb for cars. It allows people to rent out their cars directly to people. Often you can get better rates on vehicles through Turo than the major providers.