You need to do some research on the IAP options. You create in app purchases (IAP) in order to create freemium games. The game itself is free, then you can have three kinds of in app purchases:
Managed: A one time purchase - for example to disable ads in the game, or buy a map pack or add-on
non-Managed (Consumable): These are purchases that can happen over and over and are for items like potions, lives, etc... that the players will want to buy on a regular basis.
Re-occurring (Monthly): These are automatically taken out each month and are usually used for subscription based games.
The way they all work is you define a name and a price in the various app stores such as Google, iTunes, etc... Then in your game you track what happens when those items are purchased. The easiest way is to use global variable with the save system or web storage to track what items have been purchased or not. For example if I have a free app with ads, and I have an in app purchase item called RemoveAds then you put in the code (in my case I use CocoonJS) to Purchase the RemoveAds item when the user hits the button. I then set a variable called AdsRemoved to 1 and save it so that the next time the game starts I don't have to check with store (marketplace) to see if they purchased it as this can take awhile sometimes. In my code I also have a condition that checks to see if AdsRemoved = 1 and if so do not show the ads. You could also do it with consumables, each time the users purchases HealthPotion, I add 10 to their NumHealthPotions variable and save it.
You are completely in control of what your in app purchases are. You just need to make sure you give the user exactly what they purchased and be very clear on your descriptions.
The app stores that I use (Google, Apple, Nook, Kindle, etc...) all connect directly to my businesses bank and deposit the money there. The thing you need to know is that they usually have minimums. Basically you have to make over $100-200 depending on the marketplace before they will pay you for that month.