If you really have a handful of customers all the time, it is really all you need. You might even not need the feature at all. I will probably include adding attachments to the invoices a paid feature, since it takes storage in the cloud.
Thanks! I did not know Zervant. I knew thinks like Freshbooks, Hiveage, Quickbooks, Hiveage and many others.
The main differentiator being probably the free tier, and even the low price for the Pro account. I have been using Xero for a while and it is embarrassingly expensive.
Also, I am planning to add AI features soon, since everyone is crazy about it :)