Quote from @Atul Mohlajee: I suspect it's a sewing machine, a foot massager, or some other innocent device.

Your renters are constantly building up the topsoil by farming in a "land regenerative" way using livestock to massage the soil. 

Do you have an advice on book or other source about the subject and the swedish market?

You have to get her buy in with some kind of trade off like bigger house plus roommate or not her dream home and no roommate, or of the $1000 rent she can keep $300 for a monthly house maid and two hour massage or $200 shopping spree or something.

This is possible with a program called a family opportunity loan, your lender should know about the program, if not then send me a massage and I'll give the contact info for a lender that I use.

In NY, business licenses are more oriented toward retail or certain services like cutting hair or massage.

My name is Magnus and i am a Swedish investor.I have 10 houses in Detroit.

A common mistake is to try to massage numbers to figure out how it MIGHT work so that you can rush into a deal just to say you did it.  

I prefer to ask my local lawyer who specializes in landlord/tenant law and has leases that they used for decades on thousands of cases and they have been changed and massaged for local rules.  

My name is Hampus, I am 22 years old and live in Sweden (in a suburb around 30 min north of Gothenburg, if anyone here knows Swedish geographics).