First impression: You're probably fine.
Long answer (and keep in mind I'm not a pro when it comes to brewing water): The general rule of thumb is that if your water tastes ok, you're probably fine. Other things I would consider are whether you have any build-up on faucets, or whether your glassware shows signs of something like rust. But even then it is a guessing game. Can you get your water tested (you said you'll know your water composition soon, so I assume yes)? Without knowing what you're starting out with, you don't know what you might need to filter out. Figure out what you've got to start with. Without that, I don't think we can do much besides recommend you go with an RO filtration system because that gets us to a point where we know what you have.
Backing up a little further, are you planning to brew all-extract? Will you use steeping grains? Will you do some amount of mashing? You mentioned going all-grain but the way you phrased it was a little ambiguous. If you are not preforming a mash, then it doesn't matter as much, as long as it tastes good and is potable. If I were in your shoes, completely new to brewing, I think I would start out with at least a couple batches with malt extract and bottled water (actually that is close to how I started out). There is plenty of equipment overlap so it isn't like you'd be paying for a bunch of gear that you'd never use again (unless you decided to start brewing a different volume of beer, but I'm not going to get into that). Brew a few batches with bottled water and start adding a little of your water as you go until you're about 50/50, and see what that is like.
If you're insisting on going all-grain right from the get-go, then as much as I hate recommending extra gear right away I would recommend you do some extra filtration (though I am reluctant to recommend a RO system). But, as I said earlier, the biggest thing is to get your water tested.