Goodwill and Salvation Army stores and other such charitable retailers
Supermarket, drug and chain store toy sections, especially around Christmas
Some hobby stores have discount bins, though we are losing such stores
Look for nearby local hobby clubs. Members always have more models than they can build, and we'd love to share our hobby.
Family members - who knows what stuff they have forgotten in the attic or basement
Veteran's associations - vets oft enjoy having someone build something to remind them of their service; they might even buy the kit for you. I've built several for my father, plus one for my mother who didn't serve - the ship was named for the town in which she grew up.
So get out there, while keeping yourself safe, and find some fun!