Getting a Business Name Registered

Getting a Business Name Registered

Hello everyone, I am 21 and live in CA, I am now jumping off the deep end and ready to start my career in Real Estate. My questions are:
1)What is the easiest and most inexpensive way to get a DBA name registered?
2)Is it absolutely necessary to get a business name before starting any deals?

Thank You ALL for any contribution, it really means a lot!

PS: If anyone is conducting business in the San Luis Obispo Area, Please contact me at: gregpalmer33@****


Gregory B Palmer