You'll need to take a Lawyer or a very skilled translator to your local Obstina, where you can begin the process of applying for Guesthouse status with the Council, the Tourist Board and the fire dept. You'll need to buy and have registered and programmed a Cash Register (Kashapparat?).
You must have a service contract for the cash machine and you'll need an (preferably) English speaking accountant.
Many taxes must be paid for a range of things, how many beds you have for rent? How many rooms?, To set up as B&B, you have to pay for the licences, you'll have to visit your Obstina at least 5 times and they will want to come out to do an inspection of your house. You must have an official notice outside the house with your star rating and status on (yep you pay separately for that too). You CANNOT
open for business as soon as you start applying but only on receipt of a temporary licence.
Good luck,, we had our first paying guests last month.