Maybe build a mobile first web app.
If you are really wanting to provide native you could use something like PhoneGap and then you can expose to both markets.
Then if the demand was really what you expect you may have generated enough revenue by then to just get a native app for say Android and iOS built by specialist developers for not much money. If you're app is simple and catchy then it could be low cost to fund that way too.
Just my two cents of course.
