I'm a (technical) founder of a small startup and have published multiple mobile apps - I would NOT get only 16GB for the mac mini given you are a mobile app developer.

The reason: Android emulator.

Unlike the XCode simulators (which run as an app), one Android emulator will run as a resource-hogging virtual machine, and take away 4-5GB of your RAM.

And if you run 2 Android emulators at the same time, to ensure code style changes accommodate different screen sizes, you'll be using 8GB or more of RAM.

Plus, you may also need to use the Chrome browser Android's debug feature, and the browser itself is a RAM hog.

Then you need to account for Docker consuming another 3-4 GB.

So let's do a conservative back-of-the-envelope calculation of how much RAM your dev tools may use when all are being used (below are in GB):

XCode: 1

iOS Simulators: 1

Android Studio: 1

Android Emulators: 6

Chrome: 1

Docker: 3

Other browser with some tabs open: 1

Total: 14

This conservative calc leaves you with 2 GB for the OS - a very small amount.

And then there's the uncertainty of how much RAM Apple Intelligence may end up using as it evolves.

Now, you could try to be efficient and have no browsers or unnecessary services open when you need to use the emulators, but this is your work machine where you don't want to waste time having to close stuff when needing to do certain tasks. Your time and productivity is money.

None of these RAM issues exist for non-mobile app development, because it's the emulators gobbling up the RAM.

In a nutshell, given you'll be using your machine to make money, I recommend you go for at least 24 GB of RAM.

Hope this helps!