You do not need to do anything with EOT unless you provide services such as breakfast or cleaning service etc while your guests are renting your house.
You only declare your rent every time you have guests, you apply electronically to taxis.net the amount that you received in your bank account and your guest leader details (full names, passport number, their address wherever they live).
To do so, you just need to have the energy certificate (energeiako pistopoiitiko in greek) otherwise you will not able to declare the rent. Up to 12.000eur from rents income yearly, you will be taxed 15% and over 12.000 you are taxed 35%. The goverment is supposed since last year to provide unique registration numbers for the owners and those numbers will be shown next to your advert but this is still pending although they have announced this rule over a year! They also said that we are not allowed to rent more than 2 properties under the same AFM (Greek tax registration number).
Truly, it's a bit of a mess by the time they make up their mind ...
Myself, I apply the rent as I explained and I bear with you!