Sport, Home Depot is like 5 times as much. 20' isn't that much. You'll use it up, I guarantee it! I have them cut it into 80" lengths and put them on a old bed spread inside the jeep at a diagonal. They are coated with some kind of rust preventative(that has to be ground/sanded/wire brushed off before welding) . I was thinking about making a support that plugs into the front receiver that would support a longer length of steel. Unless you have a full length roof rack, don't put it on your roof. It whips and is hard to tie down to survive hard braking.
I started with one grinder but added 2 more over the years. One has a flap sander(use it a lot), another has a cutoff wheel. Both of those are DeWalts. The 3rd is a HF with a wire wheel on it. I leave all of the plugged in at the welding table.
I bought my chop saw at HF but have seen used ones at tool repair shops that people brought in for repair but never picked up.
You can buy a old school helmet for cheap but auto darkening makes welding so much easier. Wait for the 20% off HF coupon and catch them on sale.
The magnetic "clamps" are super handy also. Definitely catch these on sale also. I think they have 2 sizes.
http://www.harborfreight.com/welding/welding-accessories/6-1-4-quarter-inch-multipurpose-magnet-holder-1939.html