Radiator Rusty on Bottom, Do I Have to Buy New One?

Maybe you could use fine sandpaper to remove the rust and repaint it, I've seen radiator paint, there are some nice colours available x

I would go along with what Nina said. I have painted radiators before, they look so much better. I would make sure there are no leaks causing the rust before sanding. If the metal has worn away the sanding could do more damage. But light sanding, wipe down and paint should do the job.