How do I get cydia for free - Apple iPad Mini

Cydia is not an application that you can download. It comes as an install package via a jailbreak application.

If your iPad was properly jailbroken, Cydia is automatically installed on your device. If you do not see Cydia as one of the Apps, either it was never properly jailbroken or you accidentally deleted the app. In either case, go through the jailbreaking process again. Make sure your iOS version is supported by the jailbreak program.

Also, anytime you update your iOS version, you will lose your jailbreak. It's never a good idea to update iOS unless you know the new version is supported by the jailbreaking programs. Also, never update OTA (Over the Air) aka wirelessly. ALWAYS update your iOS by plugging your device into a computer and doing it through iTunes. Doing OTA updates sometimes has crippling effects.

Unless you used an original version of the PanGu tool, Cydia is installed by default with most all Jailbreak methods. I would recommend restoring the OS and then Jailbreaking again using PanGu (PanGu iOS 8 jailbreak tool pangu io)... assuming you're on iOS 8. Leave a comment if you're running an older OS.

Finally, a great site I've found for Jailbreak how-tos is
iClarified Apple News and Tutorials

This won't be in the regular App store and is only available for "jailbroken" iPads.

To use Cydia, you must first jailbreak your iPad.
Make sure that jailbreaking is legal in your country and you must know that you will lose your warranty.

You can not download cydia, you must jailbreak your ipad and than cydia will appear.
Make sure that jailbreak is legal in your country and you must know that you will lose your warranty.

I'm not helping you break the law. Sorry.

The only way to get Cydia application is by having your device jailbreak.
If you already have your device jailbreak, and you still do not see the Cydia; which would be due to an error on the device or the IOS version you used.
What you should do is re-jailbreak and from the options just tick on install cydia only.

I do hope this information would be helpfull for you

It's not expensive just buy it.

There's no Cydia on Android. You'll have to go to Andoird Market, Amazon Appstore, or other app markets. Also, you can install just by downloading the .apk file to your handset and running it.