GST on interest received on finance provided to customers?

I am in the business of providing finance to the customers. Until, pre gst period, we made payments to the creditors of our customer on behalf of such customer and in turn charged interest to our customers for the finance (short term unsecured loan) provided.

My questions are-
1.Can we continue providing such finance services by making on behalf payments? If yes, can we also make payments on behalf of customers located in another state?

2. Would gst be attracted on interest charged to customers located in another state?