You're right - anyone under the age of 21 needs to have a guarantor - this is an insurance requirement for most landlords, so applies to us and to most other agencies we know. Also, the minimum age someone can be bound by a contract in the UK is 18, so for that reason most landlords will refuse to rent to someone who is younger than that. You're also right that this isn't on our website, as there's no hard and fast rule, and different property owners have different requirements. For that reason we go through property-specific requirements with people BEFORE they attend a viewing so that their time isn't wasted. I'm pleased that happened in our dealings with you.