Belgrade has a number of quite decent hotels which are close to the departure location and to the city center at the same time. Price for bed and breakfast is approx. €20. There are a lot of interesting things to see here and those 2 days won't be a loss. We tend to host as much people as we can at our homes (for free, as guests) to save you from additional expences. That depends on lot of factors, so keep hotel in mind as an option and we will see what will happen.