I'm sure you've heard it again and again, but university really isn't about learning topics or skills. Many classes are a waste of time, taught by TAs that might not even grasp the subject they're teaching all that well. I definitely skipped a whole lot of classes and instead spent the time in the library getting lost in the stacks finding random books to read on my own. Once you hit the upper levels and find a major or two with professors you love that changes of course, but it definitely happens more often than most admit.

The main thing you can't replace is everything else, like meeting really smart people that are working on things that are totally foreign to your day to day studies. Maybe you walk into a room at 11pm on a Tuesday because you hear someone listening to music you've never heard before. Or someone brings you to a reading of an author and the discussion makes you reevaluate beliefs you didn't even know you had. Maybe you take a class for a gen-ed that you just know will be terrible but the professor ends up being amazing and becomes a mentor to you. Or maybe you stay up for 24 hours straight with classmates studying for a final and somehow you all ace it even though you really thought solving problem 3 was going to kill you.

It seems like you know that network is important, otherwise you wouldn't be attempting this experiment, but there really is no replacement for spending four years forcing yourself to be exposed to tons of new ideas and people every day.

There's no other time in life you're allowed to do whatever you want surrounded by so many people in the same situation as you. Money can wait.