If zoning doesn't permit business leases, you can always have a real estate lawyer draft up a suitable NNN Residential Lease with Sublet Options... you just have to make sure it's worded plainly and with enough residential language to keep the city happy should they come knockin. :-)

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

Blanket loan I know is a popular option but I don't know at what scale that is suitable or not.

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.

In need of major repairs and is not suitable for living due to some fixing that are safety issues but has potential?

The lease allows for visitors.  

I personally hope to meet like-minded people from BiggerPockets, to be able to exchange ideas about real estate investments in general and to build up a network.I am currently trying to find the most suitable investment strategy for me and the European market.

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?