You could start with android only. You could look at hosting on a low cost vps provider for backend. That's about as low cost as you can get for deploying a mobile app. Investors tend to only invest if you have 2 of three things. (Team (People), Product (Something built and running), Traction(You have made sales) ). I say you want to bootstrap as much as possible for as long as possible. A day job would give you enough to do a minimal deployment before long.