You have a mortgage of €180k @ 1.5% interest, means that you are paying less than €3,000 a year in interest.
You are getting €12,000 a year in rent.
So if you keep it you are making a profit of around €9,000 before expenses and taxes. (The rest of the €860 per month is reducing the balance on your mortgage, so it's a form of saving.) Or about €4,500 after expenses and taxes.
If you sell it, you will have around €50k cash.
YOu can pay this off your home loan and save around €1,500 a year in interest - assuming an interest rate of 3%.
So I think you should hold onto it.
There is a small kicker in that Pepper might offer you a deal to pay it off early. Why not ask them?
Brendan