In order to figure out how much it will cost, you need to know how long it will take. The amount of time a software project will take could vary from 1 day to 10 years. Even an iphone app could take that long. To estimate how long it will take, you need to have a clear functional specification. If you expect to go onto oDesk and eLance and say "I have this idea for an iphone app, can you implement it?" -- you are wasting your money.
If you aren't technical at all, I would recommend hiring someone to just write your functional specification. Using that you should be able to estimate how long your project will take and comparing to hourly rates, figure out what is reasonable (i.e. you don't want to take the lowest bid. You will get what you pay for).
Also, an android app and an iphone app are two separate projects and may take different amounts of time. For example, the Trello app on the iPhone took about 4 months of 1 developer's time to get where it is today. However, the Android port will probably only take a few weeks with two devs working on it.