As mentioned before, all Finnish apartments are normally rented without any furniture. The exception might be a kitchen top, a wardrobe and other big embedded things; and also bathroom fixtures and a freezer and stove. But otherwise there won’t usually even be lights (except possibly in the bathroom and kitchen). Same goes for basic household stuff like plates. Of course this is all not some hard-set law and there might be exceptions, but this is generally what is universally expected by landlords and tenants.
For this reason, the Finns generally move with their own furniture, and moving companies making the process relatively pain-free are an important cottage industry (just Google for muuttopalvelut). But for an immigrant bringing much furniture from abroad will likely be too expensive and impractical, so it would be easier to buy it all here. Personally I never really owned almost any furniture of my own in my St. Petersburg years, which was good since this meant I didn’t have to spend time and nerve cells trying to get rid of it before the move.
Paying rent for the apartment is a rather straightforward process: just do a bank transfer of the specified amount, to the specified account, with the specified reference number once a month. Pikipruukki housing company gave me an invoice with dates and amount of payments up to mid-2019. I actually already showed it in the post about banks. The due date is the 2nd of every month, and the amounts are all the same, although they increased a bit (for 6€ of so) since March 2018. I’m doing this payment with online bank, and it’s really easy, having defined it as a payment template (maksupohja). The due date comes two days after my monthly salary, so this is quite a convenient date.