SSL and Multi Sites in Network each with own Shop

The design i am going for is my main product site with a shop so people can buy my products. These will be individual sub sites in the network and each of them can have there own shops to sell their products. I want to be able to keep my cost to a minimum and my clients costs negligible. Nuub to Shops, accepting payments and SSL. Any and all advice on how to set this up is greatly appreciated.