Looking for 3-4 pcs, in the future need for 20-30 pcs so a plus if you have this type of quantities at hand. Located in Finland,

Eh, people are not interested in any blockchain by this logic, if you refer to price action. Monero is not doing anything special, just going with the flow.

There's no API to monitor this miner, right?

I would prefer this miner, but need the monitoring to work (checking if it's dead or not). How would you do it?

Of course its worth it, mining is a competition between producers and those with cheapest resources will profit.

Looking for second hand mining-gpu:s  GTX 1060 or 1070.

Up to 100 x 1060's or 50 x 1070's. Preferably inside Europe. Also motherboards can be included if you wish to sell whole farm.

Collection would happen in person and payment in fiat.