Many young horses work very well for beginners depending on what you plan to do with them. For a good dispositioned, young horse, the biggest things they are missing are confidence and experience, and those comes from age and hours under saddle.
If you're going to spend all your time in an arena or riding in a group with experienced horses, you shouldn't have much problem. If you're planning on trail riding alone, plan on lots of time working with the horse to get that confidence and experience.
In any case, take your trainer with you and try riding the horse in all the situations you are expecting to ride (ring/trail/alone/group/etc).