Free Domain Name Generators
https://domainscope.com
https://www.namemesh.com
https://instantdomainsearch.com/
https://domize.com/
https://www.shopify.com/tools/business-name-genera...
I do not think that it is needed to write detailed how to use them. You write the keyword you want, and they search for relevant results. All of these generators will give you different results.
Auctions For Domain Names
Most of you have heard websites like Flippa and GoDaddy again. These websites have live auctions of domain names where you can find great domain names for a low price if you are lucky and patient.
Many domain flippers have not the patient and the experience to keep their valuable domain names for a long time until someone pays a fair price. You are not going to find a domain that worth thousands of dollars for a few bucks. But you may buy for 50-100 dollars a domain that should be worth 500$.
Expired and Deleted Domain Names
Expired and deleted domain names are the domains that their owners do not want anymore. Expired domains are sold on auctions or premium listing, and deleted domains are available on your registrar. A free website where you can find them is the following: https://www.expireddomains.net/
Below is a link for more details on expired and deleted domains.