I'm doing something similar for a project I inherited from an outsourced company. Did you end up just giving it to your employer? Did you ask for compensation for all the non-work time you spent building it?
I was 23 and had a lot of time on my hands, and I was learning stuff and getting away from having to be on endless support calls with that gawdawful mess that I replaced. It was a pretty good trade, all things considered - I think I got a 15k raise that year, and built a lot of trust that I could do good work independently without a lot of oversight. On balance, I think I've been more than compensated for that time since then.
