@royconnolly
You need a rental permit, for that you'll need to provide Proof of Ownership: A document known as "List nepokretnosti" (LN) from the local land registry office. If the property isn't registered yet, a notarized statement confirming ownership is required. ​And Usage Permit ("Upotrebna dozvola"): For properties lacking this permit, an electrical safety certificate ("Atest") issued by a licensed engineer is necessary. ​
You need to pay the applicable administrative fees, which may include a registration fee (€2) and a categorization fee (€5 per room/apartment, €20 for a house). ​
Inspection: Municipal surveyors will inspect your property within a specified timeframe (e.g., within 15 days in Tivat). ​
Permit Issuance: Upon a successful inspection, you'll receive your rental permit, valid for three years. ​
Most painful part of managing short term lets : the Guest Registration Obligations.
You're required to register each guest with the local tourist organization within 24 hours of their arrival and pay the tourist tax. If late with this, you will most likely be fined, 100 or 150€ for the guest, and the same for the owner. And they are not flexible.
You must maintain a "Guest Book" ("Popis gostiju") and a "Complaints Book" ("Knjiga žalbi"), both of which must be stamped by the municipality. ​
Penalties: Failure to adhere to these regulations can result in fines ranging from €150 to €3,000 for individuals and legal entities. ​
If you decide to rent long-term instead, let me know, we are specialised in the intermediation for this. You should get at least the same annual income, without all the hassle.