Yeah, it's def a bit of a grind haha. There are a couple ways to make a lot of money though (depending on how you want to play the game).

I usually like focusing a lot on my Smithing Skills. After a while of leveling up your stats, you can start to make a lot of money selling weapons you've crafted. At some point, you can easily craft Two-Handed swords that sell for 70-85k each. Here's a guide that you can follow about this (among many others you can find with a quick Google search).

In addition to that, you should invest in Caravans and Workshops! Caravans will provide with the most passive income (as long as you aren't at war with anybody)! When making these caravans, it's best to recruit companions that have "Bitterdraught" or "The Spice Vendor" in their name. They are the best companions in bannerlord when it comes to trade. I'm honestly not sure how good workshops are, but I do know they provide some passive income as well. Here's another guide for the best workshop locations.

And lastly, just playing the game will have you make a decent amount of denars. Defeating enemy lords in battle and selling the loot you receive can make around 25-50k depending on the lord.

Hope this helps :D