Q: Are older versions of APPs available for iPad users with iOS 5?

This explains how to get older versions if they exist.

Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support

In some cases there are. See here: Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support

The step those instructions miss is:

In iTunes on your computer, download the App you want a compatible version for using the same Apple Id that the iPad has for the App Store. For Paid Apps its best to consult with the App maker to make sure there is a compatible version. With the App Downloaded to iTunes on a computer you can go into the App Store App on your iPad, Tap on Purchased, and Look for the App there. Tap on it to begin the download. It will likely say its not compatible, but if there is a compatible version it will offer to download it.

Read here: Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support

As I said, buy them on iTunes in a computer, and then download them to the iPad.

For Paid Apps its best to consult with the App developer to make sure there's a compatible version available before purchasing.