What should I check before paying a deposit on a bed space in the UAE?

See the room and bed before you pay anything. Ask what the rent covers, such as water, electricity (DEWA) and internet. Ask the deposit amount and get a receipt with the date, the amount and the landlord's name and number. A fair deposit is usually about one month. Do not pay only cash with no paper. Ask if the housing is licensed for sharing, because illegal partitions in Dubai can be fined and you could be evicted. If there is a proper tenancy, it should be registered (Ejari in Dubai). Take a photo of the room and keep any message where the price is agreed.