Adding custom field in a order a product process

Question

I am developing a site in which user can recharge his prepaid card. So Card will have a handling charge (in magento terms product price) and the amount to be added to his card (This will be the custom field).

On product view page I show the text box to fill the recharge amount. So once he move to add to cart, handling fee and recharge amount to be carried to cart. So I should add a custom field into cart process.

I am referring this blog:

I have below question and can not find answer. Can some one please help me.

1. What are the tables involving in this process?
2. Will it impact any problems if add a custom field in order process?
3. Is it acceptable to add a custom field?
4. If yes is there any guidelines to add a new field?

Thanks in advance.

Answer 1

I think there is a better approach for your case: create one product with a price of $1 and with that you can have any number to credit your card. The customer can change the amount by changing the product qty and that way you already have most of the work done without coding a single line.

Then you can add a custom field to the order itself with this answer and use it as the Card number.