I'm a Bulgarian and have few friends (also Bulgarians) who rent their flats in Plovdiv. In Bulgaria, in most cases there is no contract, it's all on good will and you have to be very careful who you are letting in your property. When you meet the person and he/she doesn't look one to be trusted, simply tell them you are waiting for a response from a person who previously called you about the property.
A scenario like yours is common here, especially in Sofia. You don't need to ask for help anyone you don't know or anyone you met in the pub. Just ask the p olice for assistance if needed. Most tenants will pack their bags after they realise they can get away with the bills.
The people you have to be scary of have their own castle like houses and don't rent flats.
There is another possibility too - the tenant ran out of job and can't afford to pay you the rent. He thinks he will... but probably next month. And then the month after that.