Airbnb is an option for the hold period that you describe, but who will clean the bathroom and wash linens between visitors?

With a record-breaking number of visitors last year, employment gains were highest in leisure and hospitality, the sector gaining 10,600 jobs. 

You also have four individuals which increases the number of cars on the property, more visitors, higher likelihood of partying, more inter-personal relationship problems, more wear-and-tear, etc. 

It also did not have anchor behind it that drew millions of visitors per year in traffic.

The lease allows for visitors.  

Since it takes so much to take the papers and start running my apartments I consider now starting a business where I can deduct all my expenses like the homes fixing at the beginning and the future properties that I consider buying but by doing this plus the short-term renting that I consider with tourists/visitors I feel more risk exposed since I will have to pay for a business loan with 6% interest, and an accountant to keep my business papers which will need another 120€ Monthly(that's for a Private Company which is considered to give a legal protections since me as an Individual is not exposed similar to protection that an LLC provides at the USA.)What is the community's opinion about what will be better for me? 

Second; Most of the Open House visitors will NOT become your client.

(even when they don't fill out a contact form) as well as visitors to your competitors.

In Kauai they call it the Visitor Designated Area and anything you buy in this zone is approved by the county.

Well, the boarders and their visitors often take the curb space in front of our rental house.