Adding nodes to raft integrated storage

Currently we are planning to use raft integrated storage with single node.

Can we use a single node raft cluster initially and later add additional nodes.

Also one query, if we have multiple nodes
does vault be able to load balance the secret read requests across these nodes or will it send only to the leader node.

Can any one help me with these queries

You can add more nodes later, you want an odd number of nodes to be part of the cluster. Min=3, anything past 7 is too many.

No, vault does not load balance, you can use an external load-balancer to distribute the requests, the nodes will forward any write requests to the leader node.