Does using text properties cause memory leaks?

(I'm assuming you're talking about Java or .NET.)

will that not result in a massive memory leak if my application makes allot of changes to the text box

No. It may require many strings to be created, but they can then be garbage collected when they're no longer relevant... so there's no leak.

You need to be somewhat careful about how much garbage you generate, but in the case of a UI the garbage collector is likely to be significantly faster than the UI anyway - I'd expect that you'd get to the point where the UI is failing to keep up with the changes before GC churn becomes an issue.