Do you *have* to work with the mafia?

[Michael_Emouse]

I thought I'd decided not to work for the Sands but I got killed (even before Varga showed up). Do you have to work for the mafia on or get killed?

[geocapital]

Hm... I dont remember. But I think you need to keep them relatively happy. So, work part-time with them.

You can go after them later in the game, so you have the chance to rid of them for good.

[braindeadpizzaslice]

regardless if you help kendrick or not you will end up as a member of the mafia yea

[I'M NUCLEARRRRRRRR]

You can refuse all three of their first tasks but I believe you have to buy one of their services in addition to responding to all of their favors to prevent them from killing you, you dont have to send any detectives or police to the crime traps and I believe giving them money from buying it will keep them happy enough that they dont shoot you. I wouldn't recommend this unless you're going for the no one left behind achievement because you are going to have to directly help the mafia in doing illegal things later in the game. making it impossible for a "clean" run

[Padelboot]

Pretty much what has been said before. You at least have to keep them happy enough not to shoot you. Thankfully they are super clear, when their patience runs low and you will know soon enough to make it up.
There are multiple ways to achieve this. Responding to their side quests, selling goods you found (if the profit is shared it also boosts your relations with the police station) and ignoring the calls they want you to ignore. You have to decide yourself how far you will go.

As has been said, you can take down their organisation later. Until then keep your head low and strike once you get the chance. Once the big one is arrested, you cash in a lot of money and don't ever have to bother with the mob again. They also tend to get way less active in arc 2, giving you more room to breathe.