What happens to my paid apps if I do a factory reset?

Re: reset to factory settings

You can easily download your apps again from the play store
 
Re: reset to factory settings

Whenever you purchase an app it saves under your Google Account, as long as you have that Google Account, resetting your phone to factory settings won't stop you from getting them again.
 
Re: reset to factory settings

No, you don't need to pay again for them.
You can also switch your device, only the Google account must be the same. :)
 
Re: reset to factory settings

Your game progress won't necessarily be saved, though. It depends on if the game backs up its data to your Google account, or to its own server. If all of the data is locally stored, then you'll lose that progress. You could consider backing up your app data using Helium, before you do the factory reset.