How do i get rid of mice from coming inside my house?

okay, so i just moved to Palmdale, Ca and i have a PROBLEM ! I have mice in my house, and i want to get rid of them ASAP i literally cant sleep at night... I'm constantly cleaning and making sure everything is organized and put in place... please can someone please help me on some tips, on how to get rid of them! i cant afford to pay a terminator.