You have not defined what kind of game. You know sudoku would probably the easiest as it is just text. But hey even card games are possible. I have a spider solitaire in the making. The index.html (which has all graphics inside the html) is 175kb, the js file is 17KB , the css is 7KB and since i use a special font, the font file is 19KB. So with that i'm below even 1MB overall and i did not zip it yet. To be fair, its not complete yet, but the main game is finished, its just all the side stuff, like option menu. And as you can see with the small js size, adding the missing code will not expand it much. It will be even smaller at the end, because it is before minifying (which is where i stopped) . Although i skipped audio, which is like pictures a bottleneck.
The last question of yours is a whole other topic. I do it as a hobby, so no, i will not bother about money. Earning money in the gaming industry is very hard, independent which limitations you give yourself. If you deliver a great game, you can earn some, but the way to that is long. Not wanting to discourage you, but checkout some people what they say about the industry or even try yourself to get some attention for your games and you will understand.