Startup Idea: Pay-as-you-go Payroll Software for Small Businesses

Startup idea to develop a payroll application for small business owners, similar to Quickbooks, which allows them to quickly pay their employees on an as-needed basis without requiring a monthly subscription fee.

I am an adminstrative assistant for a small retail store. I sometimes use extra employees and I would like to have an app that I could quickly pay them, similar to Quickbooks payroll, that does NOT require a subscription because I don't want to pay all the time, just when I use the service. I have yet to find that allows to to run my business this way. Yes, I have tried ADP, Quickbooks, Square, and they all require subscriptions.