Will you be coming here as an international student? If yes, then you have to keep a close eye on your finances. You don't want to be living in a big room. It won't matter. Also, if it's a big room, it will definitely cost you more. So look for a mid-size room that you can afford well.
About the place, you should always check how far it is from your school. The near, the better. You also wanna check for bus routes that will take you to school regularly. Yes, many landlords demand a security deposit which they will return when you will be leaving the room. It's always refundable - unless you were involved in some property damage.
Regards,