New and want to build my first bike.

I've never owned a bike. But I've always wanted one. The problem is... I have a small budget. How wise would it be to buy an old cheap bike and redo it or buy a wrecked bike and repair it and do what I want to it. As long as nothing is bent and such.

I know my way around vehicles pretty well as I've worked a several mechanics shops and autobody shops, and I feel I would enjoy my bike more if I didn't just go buy it something and never put myself into it

Thoughts? I'm 24 btw