How to get analytics for sponsored ad?

[Jake]

There is ad hosting software that handles the impression & click counting, in some cases the client may be able to log into a control panel to check status. Showing sales/conversions is trickier, in the case of affiliate marketing, some merchants allow affiliates to place "Pixel" code on the sales thank you page that registers sales, that ad management software probably accommodates such code if you can get your clients to install it.
An additional service you could offer is ad retargeting, you would set a cookie in the visitor browser when they first click the ad and use some ad network that supports retargeting to show more ads around the net.