In order to make money from free Mobile apps you need to make sure you understand the various options available in which you can release your mobile app to the general public.
Freemium Mobile apps
The key is not to give away all the best features that you have in stock for free. Freemium is a version that offers free features, but in order to get the really juicy stuff, users needs to update to the Premium version.
Advantages - Users who have tried the Mobile app before buying it are more likely to pay for the premium version when they discover that the app fully satisfies their needs. Also Freemium Mobile apps allow you to develop a large user base that you could re-sell to.
Disadvantages - Your users might get bored with the lack of features if you aren't generous enough and might end up uninstalling your mobile app. On the other hand if everything is free then no one will upgrade. So you must find the right balance in order to create the need for update and not its suppression.
PREMIUM MOBILE APPS
The Premium Mobile app version is based on the Freemium Mobile app, users always have a access to it. This version is of course not free but, offered via the Freemium one. A customer that wants more needs to update to the Premium version of the same mobile app. For example, for Music apps, if your users want to listen to your music off-line and not have to be bothered by commercials every now and then, they have to subscribe to it to your premium mobile app.
This model looks a lot like the freemium strategy, however a subscription lures users with content instead of features. Apps that offer subscriptions create an amount of revenue per user not to mention that apps which use subscriptions earn up to 3 times more money per user than apps that rely on advertising or paid downloads only.
Advantages - Subscription results in a constant and repeated revenue stream so you can rest assured that revenue keeps flowing in steadily. You have to continually offer high quality content to retain your users and/or offer a newsletter. It also leads to loyal and engaged app users, someone who gives you his/her contact is willing to know more and get engaged.
Disadvantages - You must find the balance between the free and the subscription content, this can be hard to determine. Also Subscription requires a lot of commitment from a first time user, as subscriptions have a reputation for being hard to cancel, people are afraid that they will get messages on their mail boxes twice a day or spammed regularly for other reasons.
These apps allow users to use a free version of the app but offer the possibility for additional, optional, paid features. Most of the free games on the app store are free, however, in order to get further and faster in some Games you are allowed to buy extra lives or extra points. These kind of offers encourage users to make purchases often because it can help them reach their goals faster within the game similar to what Pokemon Go does.
Advantages - It really works well for games and when users buy virtual goods/items it leads to better user engagement and long session times because users will return to use their items.
Disadvantages - You don't get it all, the mobile stores (Playstore or AppStore) where your app is published will take about 30% of the profits from in-app products. Also, users may be less inclined to download your app if they see that it includes in-app purchases, it might make them feel like it's too expensive for a mobile app.
Advertisement Supported Mobile applications
In app advertising - Advertisements in free apps can help in generating revenue from your free Mobile app. The key to make money via ad support networks is to bring in the traffic. The price is mainly defined for click-throughs, impressions, the format of the ads and also the type of the ad. A video ad will of course cost more than a simple picture ad. Keep in mind that high traffic and many download are going to be needed to make a decent profit from your free mobile app.
Advantages - It works well if your app is a new concept to the market. The more traffic you get the more money you will earn from ads. Usually at cost per click.
Disadvantages - It generates a very small revenue per user so you need to get a lot of traffic and work on the marketing front of the ad.