Is it just more or does it take an insanely long time to get boxing up. I feel like you have to level everything up at the same time eventually to do the things you want to do in the game, I don't want to fight and box when I just wanna do drugs or what ever. I'm 8 hours in, got a house for 2k that I can't find and that's about it. Boxing is at 6 and hacking is at 41. Combat skills are around 10-14 everything else is 1-5 besides any of the stuff like drugs I actually wanna do. Also can't even find who is willing to buy drugs. Don't get me wrong, I looooove the idea and gameplay of this game but man the grind is insane.
You are correct that all skills tie into each other. You can certainly specialize, but skills relate to each other in important ways an ultimately you will need to get multiple stats leveled. For boxing, are you training in the gym or just fighting in the arena? Training gives you way more EXP, because it is training haha. There are drug spots and drug dealers guarding them, you need to knock them out before you can sell there. Sounds like you need to explore more and interact with more parts of the world and discover new things! If you have any questions though feel free to ask :)
As for it being a grind, it is an entirely level based grindy RPG, you are correct.
As for spending $2k for a house, do you mean you bought the empty lot? That's not a house, it's an empty lot as the name describes it. It's so you can build you drug warehouses on it. It's in the gang area, but until you buy fences and buildings, it will remain just an empty plot of land.