My take: if your side hustle needs a $15 app to track 4 invoices, you need to rethink your whole setup
I finally fired my invoicing app after it took me 3 weekends to figure out why 2 clients never got their bills, and it was because the app auto-archived anything unpaid past 14 days. A plain spreadsheet and a calendar reminder would've saved me 20 hours and $180 in late fees. Anyone else think we're overcomplicating basic stuff just because an app exists?
Spreadsheets are great until you have 15 clients and need to chase down who paid and who didn't. The real problem was your app archiving stuff without warning, not the fact that you used an app. A good tool should save you time, and if it's not, that's on the tool, not on the idea of using one.