The problem with this business is that its mostly seasonal and timing is of the essence.For instance if you were to supply maize now you will be 'burnt'seriously bcoz the prices are very high and most retailers are unwilling to buy at the moment since the rain season is about to start and farmers will be forced to reduce their stock thereby reducing their prices so as to create room for new harvest.So what this means the retailers know in a few weeks the prices will come down so they can sell their stored products as they wait for the price to come down.
I would advice you to get a good retail shop that you can use as a base of operation and then start looking for retailers who you can sell to, at wholesale prices.So you can be both retailer as well as a wholesaler.
'......to the acknowledgment of the mystery of God, and of the Father, and of Christ; 3 In whom are hid all the treasures of wisdom and knowledge.' Colossians 2:2-3