Why students go
Address is a big national chain, so their website carries a large searchable listing database — useful for browsing prices before you even arrive in Bulgaria.
Being a national brand, staff are more likely to have handled foreign clients and paperwork before, which can make the process smoother if your Bulgarian is non-existent.
Same rules before signing: agreed fee, viewing in person, written contract, landlord declaration for non-EU students — see the Housing guide.