In order to be really successful on iOS you have to make an extraordinarily excellent game (which is hard to do), license some intellectual property that your audience is already familiar with, or have a large marketing budget you can use to buy your way to prominent placement.
On Android there's a bit more opportunity - if you move quickly, you can do alright by ripping off iOS game concepts that haven't been ported over yet. Monetization is still pretty bleak vs. iOS.
Funding's available to companies who've already had some successes (although in that case you really shouldn't need to take it) or to new teams with a track record at other companies.
There are a ton of people doing this - you'll face a lot of competition. I wouldn't let that stop you if you're super-passionate about the field and your ideas.
I know of one YC company doing exactly this and doing well, although they got there after a pivot - they were accepted on the basis of something completely different.
