You need to use some kind of CRM, or roll your own system. Something with a ticketing component (so, I guess, most of them?) is probably best. Invoicing can be

You need to use some kind of CRM, or roll your own system. Something with a ticketing component (so, I guess, most of them?) is probably best. Invoicing can be whatever cheap solution. I think the HN way is rarely the best way. The best way is the way that works for your unique scenario. Many people on HN have what I would consider stupid or silly requirements, but I'm sure those people think they are really important. Similarly, I'm sure many here would say my requirements are silly and can be achieved in a much easier way. I would suggest you do not use Excel or text files as a CRM. But, you probably don't need SalesForce, either...