(and be forewarned, it is SUPER easy for any taxing agency to know what you are doing - so hiding income is pointless....   

I'm also a member at the The Landlord Protection Agency which is an educational website from which I've learned much although I did buy a membership there I think there's quite a bit of free stuff available.. https://www.thelpa.comI love this stuff, and I believe there's no better way to generate real wealth.

I would hate to have to go to a collections agency.  

@Jeffrey Hanson, check out The Skarin Agency skarinagency.com

Second step to take after reading the lease would be to contact your lanlord/leasing agency and speak to them about the about the matter. 

At the same time I'd hate to be wasting my time doing something I don't need to.Also I see how many real estate agents have their own entity (LLC) and their own website, identity sort of outside of the agency they work for.

@Kayhahn Alikhani Generally, it is best to separate rental activities from non-passive activities, like a real estate agency, flipping or wholesaling, into different LLCs.  

@Michael EncoyYou should be more pro-active: go to ALF-related events and reach out to agencies that support these types of facilities and ask for the local operators names to connect with.

Is there anyone who could recommend me a good real estate agency in Poland?

It all ended when I turned the old PM into Colorado’s Dept of regulatory agency’s.