Chunck will know better, but I am going to say yes, it's ok to mirror. As long as there is symmetry, if both sides look alike, I say mirror away. Also remember if you are totally totally new, it's best to start with The Blender Basics Course:
https://cgcookie.com/courses/blender-basics-an-introduction-to-blender-4-x
Then ideally Modeling Fundamentals:
https://cgcookie.com/courses/core-fundamentals-mesh-modeling
That way you have the bedrock knowledge and then you can branch off to all the cool beginner courses.
Thanks for respond
Yeah, I've completed these courses 🫡 But I wanted something related to games 😅
Greetings!
Like Omar said, it shouldn't be a problem! You will just need to decide how you want to mirror it. If you are using a modifier, you'll have to find the proper order to place the mirror modifier so it mirrors the correct information. Order of operation matters for modifiers!
If you're just going to mirror the final model after you have applied everything, make sure to check that your normals aren't flipped. This will cause you some serious issues with baking and displaying textures, so you'll want to save yourself the headache now if you can! We look at displaying normals direction in our final optimization video later in the series. :)