A great example is a chemist I knew that love research with selenium (an uncommon element). He was most interested in what role it plays in organic chemistry. That’s it.
But when he wrote up grant proposals it was always about the anti-cancer properties of selenium compounds. Never mind the fact he had zero plans to actually pursues that end.
Working a day job in industry isn't categorically different, except that someone is probably watching your spending more closely. You have to figure out a way to set aside some time to work on your own interest, whether you do it at work or at home.
As for money, you can get technology made for 1/10 of what it costs your employer, by choosing your battles, cutting out all of the overhead, and using free stuff.
Newton and Einstein both hit on some big ideas during lulls (@home to avoid plague for the former; patent office work for the latter).