When you look at a mobile game for iOS on iTunes, there's a very handy at-a-glance tool that lets you know whether or not it's supported by in-app purchases: a bar on the left-hand side that shows the most popular purchases.
Google Play, unfortunately, is a little less clear. You can never be sure, when you're looking at a game, if it's completely free, ad-supported, has a free demo but the full game can only be unlocked with a one-off purchase, or if it is filled with sneaky bits of content that can only be unlocked if you spend money in increments.
Honest Android Games offers a solution. It curates games so that you can easily find a game you're willing to download, and eschews anything that incorporates incremental payment models. It files them into one of three categories: paid; completely free (including ad-supported); and freemium (which incorporates a one-off payment to remove ads, or a one-off payment after a free demo to unlock the full game).
Read more of "How to find Android games with no in-app purchases" on CNET Australia.