Interested to know how far i can go without money.
There are tons of threads on this topic, I suggest finding a few of them and checking it out. Long story short, it depends on what your application is, how you built it, and how people use it.
@andrewgassen is right: it depends very much on the app you build. If all your app does is show a text field saying “Hello earth”, you can support a ton of users, whereas if your app relies on heavy use of the database, you might need to upgrade quickly. Also, some apps store information without them being accessed too often, while others are constantly updated and read.
If I am to assume that you build an “average” app, then it’s probable that you will get through the testing phase and early user adoption, and once your app reaches 5-15 users, you will probably need to upgrade.
Note that this estimate is pretty rough.