Pathfinding is only available for Unity Pro, and only from version 3.5
Unity does not support dynamic NavMesh generation/update and requires baking beforehand. There is also a limit of 1024 NavMeshAgents Unity can handle at any one scene.
If dynamic pathfinding is important to you - or you absolutely must have huge crowds in your game - you’ll have to search for another solution. If you can get away with baking, Unity does a pretty good job at generating the NavMesh itself, and the avoidance and pathing algorithms aren’t bad at all.
thx for your time. Will google for dynamic pathfind lib. But I realu surprised that Uniti does not have free pathfind feature and limits are so strong in standart navMesh. I hope in future it will change.