Determine where the sale will be located. Investigate your local laws regarding such sales. Some places restrict them to only commercial sites. But, if law allows, a home garage or other covered area works well for the beginning sale. You also need to investigate laws regarding advertising sign placement.
Some local governments restrict sign placement timing and location.
If you have family to help, you can probably handle it without a partner. If not, you may want to consider having a partner at some point in time. You also need to consider babysitting needs, if applicable. There are often long hours involved and some children may not tolerate that. You will need plenty of rack space to hang and label clothing for display.