Is it possible to require users to create account before being able to post a listing?
Yes. There is an option in Listings admin screen to only allow posting of listings once a visitor has an account.
To enable this go to Listings ▸ Settings ▸ Listing Submission and check "Submitting listing requires an account" and also uncheck "Allow account creation". This will force users to create an account separately before being able to submit their listing. If you would like users to have the option to create account while submitting listing, then check "Allow account creation".