anyone know a template etc for sending an invoice?
Check out https://www.waveapps.com/ it's free, and very good. Even handles basic accounting for you etc.
Shopify has a free invoice making tool: https://www.shopify.com/pos/invoice-generator
Freshbooks, freeish - https://www.freshbooks.com/
Harvest, also freeish - https://www.getharvest.com/
There are google sheets templates which will serve the purpose as well. I like them because of the simplicity.
I'm creating an extremely straightforward invoice app (with a time tracker straight on the invoice). Let me know what you picked.