I have two credit cards that I don’t really use and was wondering if there’s any cons to putting a small balance of $50 on one and keep paying it at the end of the month with the other card without letting interest accumulate. I was thinking of transferring the $50 back and forth for months to keep the cards “Active” but would banks have something against this, since neither card is actually being used?
Normally your bank will limit the number of balance transfers you can do onto a card. You would instead have to take a cash advance to pay off the other card, in which case you'd be paying interest from the moment of the advance, not the end of the billing period.
If you want to do this, just buy a cup of coffee (or whatever) on each card each month and pay that off before the due date.
To keep a credit card active one could use it for a single small transaction every couple of months.
Besides using it to buy coffee, one could also use it for a recurring transaction, by setting it up for that recurring transaction to be automatically charged to the card. It could be a utility bill, or a streaming bill, or anything with a monthly or quarterly charge.
You need to make it a habit to check the credit card website every month to make sure no unauthorized charges appear on the bill. Knowing that you have a recurring charge will give you incentive to not skip a month. You could also turn on alerts to make sure an email or text reminds you to check the website and pay the credit card bill.