Mandrels are cheap, especially for the 2.5" for an 80. I think I spent about $150 on eBay for 6 90* and 4 45* stainless bends (more than necessary but doesn't hurt to have extra). The easy way to practice is once you start cutting prices to fit, just start welding the scrap. Watch some videos, setup according to metal thickness, and start practicing. Also can find crap around the garage, yard, etc. My first victims we're a broken basketball hoop and and old grill, and both were better off when I was done.
I'll find some pics of what I've done, it's not always pretty but it's solid and does the job!
*Edit - when I say mandrels I mean the prebent pipe pieces, not the mandrel to actually bend the pipe, those things are very expensive which is why not many shops have them.