Hi Damian, actually the first one is gramatically correct. We don't use like 나는 많은 돈을 있어. "있어" is a kind of verb representing the state (possessing someting). In this case, we use "이" instead of "을" in general. We can use 나는 음식"을" 먹어 since the verb "먹어" indicates the action rather than the state. Well I'm not a professional teacher but anyway but just hope this can help you a bit!