I know somewhere on the internet must be a tutorial how to create such dlc. But googling didn't help :(
For example, Knight Rider mod has optional "knight" dlc with Vapid Dominator and all sorts of corresponding text files.
And I want to create a "bcsocars" dlc. What I have to do and which files should I include in .rpf? 

Edited October 15, 201510 yr by AlexVonShep

This might help you: http://www.lcpdfr.com/forums/topic/50909-adding-a-new-emergency-vehicle-is-possible-now/

Never tried to do all the manipulations myself, but it might give you a lead.

This might help you: http://www.lcpdfr.com/forums/topic/50909-adding-a-new-emergency-vehicle-is-possible-now/

It has already helped me, but I need more than editing 2-3 code files.

This might be useful for you.

 

This might be useful for you.

 

Thanks! One external link there is quite useful!

Thanks! One external link there is quite useful!

Another tutorial:

http://gtaxscripting.blogspot.com/2015/08/gta-v-pc-add-vehicles-idea-no-replace.html?m=1

I've been looking for something like this actually. Only I was wondering if it was possible to create your own DLC like in these tutorials. but instead of adding vehicles you could replace vehicles and files.

This way you could have all your vehicle, ped and whatever mods in one place.

I have seen that BXBugs' CVPI makes a "Patchday5ng" folder and places his vehicles in that.

Would something like this be possible?