I want to make a very simple app for my windows phone. Do i really need to pay & get the 19$ dev account, even if i plan to distribute my app for free ?
Yes, according to Microsoft, a paid developer account is needed to submit any app. You can submit 100 free apps once paid up.
There is Windows Phone App Studio where you can create simple apps online and is free. If your app is simple enough, that might work. I haven't personally tried it.
Windows Phone App Studio lets you swiftly build apps for immediate publishing, testing, and sharing with clients, co-workers, and focus groups. Need to make changes or try variations? With the App Studio it's a snap!
With Windows Phone App studio you can build apps. And test them on you own device for free. But to publish an app to the store, a paid Developer Account is required. With this account, you can publish app to both, The Windows App Store and the Windows Phone App Store.
Check this link for Free Developer Account from Nokia.
If you are a student, you can register as a developer to the Windows Store.
Go to Dreamspark and get registered. And then use the statements (https://www.dreamspark.com/Student/Windows-Store-Access.aspx)