Found this website that gives locations that you can get relatively quick covid-19 test and results. I would presume each location varies on times. I called the one in St. Petersburg, FL and they said results would be in 3-5 business days. This is at least a step in the right direction for beginning to travel to destinations that require you have a negative Covid19 test result. Other hurdles include quarantine where you go though.

https://rapidtesttravel.com