At work we use Storyblocks and Warner Chappell music but I wouldn't calls them low cost. Freelance work I've used NoCopyrightSounds and the YouTube Music library songs that require no attribution. Both of those are free but sometimes don't do the job. That's when I usually go to something like Pond5. Which usually is good and low cost.
@micahbp Awesome! Thanks so much...will definitely look into those!