Get the level up perk in mastermind before you start this journey if you haven't already. It's atleast level 38 I think. Cause certain levels you get 2 bonus skill points so I got it around 38-45 personally. It's more of a money issue unless you run with someone who has c4 or do good at certain multi day missions cause it's like 750k and 8 skill points.
You need to spend at least 30 points in the Technician skill tree to unlock up to tier 5, and then another 8 to ace the skill and get C4. You get 1 point per level up, and an extra 2 points every 10 levels. So you could get it as early as level 32 if you spec things exactly right. If you spend your points just on things you actually want though, it'll probably take at least until level 40 or so.
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It's hard to say exactly. I got it at level 45 but I wasted a lot of money and respeced a few times so I had the points to spend on it a few levels before but took a while for me to get all the money needed to pay for the skills. It's roughly around level 40 though.
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