Last year I visited both Pike's Market in Seattle and a pretty good sized Flea Market/Farmer's Market near or in Daytona Beach. I had a really good time at both. I noticed that several of the booths looked like they had been there for ever and some looked like they setup the day of and maybe tore down every night.
1. Location is the biggest obstacle. You need a place with easy access and room to hopefully expand. Low rent or ideally purchase price. You'd need a location on sewers.
2. I think a good mix of open air and enclosed space would be ideal.
3. Running the Market as a non-profit might work so that the booth space was rented reasonable.
4. To keep operating costs down, would need umbrella policies for insurance for all operators.
5. I am thinking about a rechargable card that people can put money on to keep credit card operations to a single account to eliminate the need for phone lines or expensive equipment for most operators. Could also use this as a revenue model. Money could be paid in at a booth and put on charge cards. Booth vendors could pay a % of their sales as their rent. No sales for the day, no rent. Very little risk for the booth vendors. It could bring a lot of variety to the market.
6. Build in a restaurant that uses ingredients from the market.
7. Have a place to get a beer/bourbon.
Any big box retailers closed down that might make a good location?