You only pay a fee of 4 euros for a successful rent collection. Creating an account or adding properties costs nothing. It doesn't matter if you collect rent for one or more properties via Bidly, the amount remains 4 euro per transaction. This includes VAT and will be deducted from the payment.
So if a payment from your tenant fails or does not go through Bidly for any other reason, you will not pay a fee.
You have no subscription, no connection fee, and you don't have to pay anything upfront or in arrears.