score:7
The embassy is more interested knowing whether you can afford to pay your accommodation costs for three months than the exact location where you are staying.
The best option would be to have a preliminary booking for a short-stay apartment or the like for the full three months, complete with a cost estimate and proof of funds to pay for it. But you could also state that you're staying in a hotel for the first X weeks, cost โฌY and here's the booking, and will look for a local apartment that you expect to cost โฌZ/month for the rest, and here's a rental site showing what you can get for that price.