Best database design practices recurring payments

I have a question regarding the 4 extra columns needed or recurring payments to work properly. Since I am using a dynamic MySQL database for my products, I am assuming that the best way to pass these 4 variables to the shopping cart is to have them added into 4 unique database fields. The 4 fields that I was thinking of adding are:

ProductRecTerms
ProductRecAmount
ProductRecFrequecy
ProductRecAmount

Would this be best practice when it comes to where this information is stored in the database?

Let me explain what I need to do. The website I am designing will be selling live insects as food for lizards and other small exotic animals. The website will offer these live food items in a subscription and non-subscription format. Ideally I would like to give my customers the option of being able to upgrade ANY item for sale as a subscription sale. My next question is, would I need to create a copy of every item in my products table, for example, 500 Crickets non-subscription in parallel with 500 Crickets subscription? Or can the subscription upgrade be handled with a separate database table, let's say a table called "Subscriptions" that in turn would store these 4 unique cart variables used to make the subscriptions work? Or would the addition of such a "Subscriptions" table be over complicating things? Any guidance in this area would be greatly appreciated.