The number of members may need to be increased to assure a reasonable charges, and thus adequate returns. It may be worth checking if any of the expenses such as rent could be waived or lowered for the first year as the market is just getting going. Some markets require that all products sold are grown, baked, caught, canned, etc, by the member offering them for sale. Others allow buying of produce for resale only if no member who grows that item is bringing it in for sale. It is up to your market how you want to handle this question.
Many markets use formal contracts with members.
These decisions are made by your market, and may be changed from time to time as your perceived needs change. Some markets have decided that they want a specified number of slots for bakers, crafters, fish sellers, etc. In any case all members should sign an agrreement saying they will abide by market rules before they attend market. Needless to say decisions arrived at or agreed to democratically by the membership will be accepted by the membership more readily than those autocratically handed down by the organizers. These are reserved for members who haven't decided whether they can commit to an entire season and who want to give it a try.