Money makes the world go 'round. That's a natural fact. It also makes things a whole lot easier in Agents of Mayhem. If you want to make all the scrilla scratch in the world (or at least a lot more than you're currently making in-game) rest assured there are plenty of ways you can start rolling in the dough today, so that you've always got the cash flow coming in if you need to purchase additional items and loot to get you through specific missions.
How to Get More Cash Quick
The simplest way to earn more cash is to simply play the game more. You've got to take out enemies, so make sure you do it as often as possible to start pocketing cash. Just like looting enemies in other games, every Legion member you fell while cruising through Seoul will net you loot and pocket change, so make sure you fight off as many enemies as you can to ensure your pockets start to jingle. You might even want to start repeating segments to save up cash and kick the same bad guys' butts over and over to keep packing more cash in.
Alternatively, tackle the side missions you can sign up for in-game. You'll have to go out and look for them in the open world areas, but they're worth seeking out since they offer cash and other goodies for your time. This may sound like a no-brainer, but a lot of players tend to ignore these missions and continue with their main campaign. Make sure you take the time to finish out these side missions and you'll be rolling in the dough soon enough.
While you're gallivanting around Seoul, you can also check out Relic's stores around the city. You can partner up with him to open additional stores throughout the city where you'll earn a small percentage of cash with each one you help to reopen again. This should help you keep picking up upgrades as well, which will help you in the long run. Just make sure you stay consistent.
Just like in real life, there are plenty of ways to earn that sweet cash. You might just become a mogul if you're not careful.