In all of these Markets you will find a Farm Supply Merchant, who will sell you seeds, water cans and fertilizers for your farm (some may also offer farm certificates and stuff like scarecrows for your farm) and a Farm Manager, who will show you a list of farms you can go to. The Farm Manager can then transport you to your farm or farms of other players and he will also let you choose an active farm out of all farm-versions you currently own.
In Paris and Bejing there will also be a Home Item Merchant in the Farm Market, specialized on carpentry. He has a lot of crafting guides for you to either produce paint or to make furniture with your own hands that you can decorate your house with, after you have built one on your farm. This Home Item Merchant also sells wood polish.