In the five years since the iPhone came out, there has been a gold rush to develop apps, but a new report shows just how hard this business can be.

Vision Mobile, a market analysis and strategy firm, surveyed more than 1,500 developers worldwide and found that one in three apps generates $500 or less a month, which means developers have to find other sources of income to get by.

On average, developers make between $1,200-$3,900 per app each month, though some platforms prove more lucrative than others. For example, iOS developers surveyed make more per app each month on average ($3,693)  than Android developers ($2,735), but both fall short of what Blackberry developers earn per app each month ($3,853).

Those are just some of the big findings from Vision Mobile's report on the state of the app economy in 2012.