So you don't use higher isos to help compensate for reduced lighting in poorly lit areas?
No. For me it's a bit more of a challenge than it should be for you because your gear handles low light better than mine.
There's an acceptable level of noise for me, that I know I can de-noise in post, still, I'm very mindful of it.
If things are too noisey I simple won't shoot there, or set up some lights.
Part of your gear is going to have to be a couple of flashes and a couple of lights with stands. It's part of the job if you're looking to turn this into a business.
You're responsible for the scene being lit adequately. Before a shoot, talk to everyone and find out where it's going to be. Try to go check the place out the night before if possible.
You need to figure out all the equipment you're going to need for each shoot before hand.
I learned this the hard way.
Don't underestimate the need to budget for lighting gear.
This game is all about capturing light appropriately for each scene. You have to find that balance.
Avoid using software to compensate for poor conditions.
If anything, in that type of situation where you felt it was too dark, just take the shot dark, and boost it a little bit in post.
In the case of the picture you share, I suspect you could have gotten a very clean image straight from the camera with the right settings though.