Here is explanation how to set properties inside "Properties" parameter:
Property name :: addtional price :: symbols color :: checkbox status

, i.e. you have to divide with :: each characteristic from others.
Property name is title of property (size, color and etc.).
Additional price allows to variate product price depending on certain property.
Symbols color is color of property name.
Checkbox status defined is proferty selected or not when seller adds a product.

Here is an example,

size - m::-7::green::1
size - s::-5::green::1
size - l::0::green::1
size - x::0::green::1
size - xl::+5::green::1
size - xxl::+7::green::1

You also may pass any of characteristics, for instance,

size - m::-7::::1
or
size - s::::green::1
or
size - l::::::1
or
size - m

There's another way to provide users ability becoming sellers - is sell them a subscrpition. Please make sure that you install Mighty Membership component and its plugins before you start to implement "seller by subscription" scheme. To learn more about Membership component you may here.

1) Create subscription for each seller type:
Standard seller subscription
Silver seller subscription
Gold seller subscription

2) Go to the section which you create for the shop and set subscription according seller level, i.e. you open tab Commerce find:
Standard sellers settings and set "Standard seller subscription" plan in Confirm Seller by subscription
Silver sellers settings and set "Silver seller subscription" plan in Confirm Seller by subscription
Gold sellers settings and set "Gold seller subscription" plan in Confirm Seller by subscription

After that you may add link (Mighty Membership -> JCS SUBSCRIPTION FORM LAYOUT) "Become Seller". Or close article adding ability in commerce section type with "seller's" subscriptions.

First of all please make sure that you use the latest versions of Mighty Commerce, Mighty Resource, Mighty Registration components. If you already have the latest versions, then please follow the instructions.

STEP 1. You need to create 2 fields more for user's account. Use Mighty Registration component' Field manager.
The first field "Seller request" should be of radiobutton type with values "Yes"/"No" ("No" is default). This field should be accessible for all users.
The second one "Seller confirmation" may be of radiobutton type with values "Yes"/"No" ("No" is default) as well or you may use any other field type, for instance, if you need each seller to have their own section (in other words seller may submit goods to certain section only) then you may use secret word for each seller, just put secret word in section parameter and user's "confirm seller" field. Please note that users should not  have access to their "confirm seller" field via front-end. To achieve that you need to set "Access Level" for "special" and set all "General Parameters" to "No". This field value will be edited by script after admin confirm user as seller.

If you need to submit sellers automatic then you may use the same field for both commerce section parameters "Request Seller" and "Confirm Seller". All you need to do in this case - just submit new seller -> STEP 3.

STEP 2. You need choose section of Mighty Resource component which will be used as a shop. And add "Seller request" and "Seller confirmation" fields to "Seller associations" section parameters. See tab Commerce.
Please note that you need to create different associations field if you want different sections to have various sellers.

Now to become seller user should edit their account - set "Seller request" to yes and wait while administrator confirms their request - STEP3.

STEP 3. Administrator goes to Mighty Commerce -> Requests sellers and confirms sellers.