So I'm a bit confused on what you are doing or trying to do.
You asked about getting a duckling (or more) as a pet and really only want one.
Then you mentioned a friend gave you her ducks
then she hasn't given them to you yet
and then that you will get them in the summer
Are you getting ducks of your own or preparing to take your friends ducks this summer?
Does your friend have her ducklings now? If so, they will be full grown by summer and you will be dealing with full sized ducks.
If your friend just got ducklings and no longer wants them, now is the time to start listing them on CL and at farm stores since people are adding to their flock in the spring.