It's pretty simple really. Check the floors which have smelly rubbish compartments. More people = more mess, particularly students.
Check the electricity/water usage. Fail-safe way. Raid, kick them out and repeat.
The 'Pro' of being available to foreign investors is only true for the original purchaser. After they settle on it, the property is now considered 'established' and is therefore not able to be sold to a foreigner as an exemption.