Question about payday 2

Just got the game and I hear there's no vac ban?
How's it work? I don't want a vac ban on my main account

There is no vac ban. Maybe if you are stupid and use it online people can report you. If you want to farm achievements solo is ok.

I only wanna use hacks to get some money to buy weapons, that's about it

How about DLC? I hear you can get free DLC? or is that bannable. sounds too good to be true since DLC costs $$

It's basically pirating, so yes you can get banned albeit unlikely. Then again, everything related to scripting is at-your-own-risk. That includes getting money to buy weapons.