I am in the process of buying a 99 lowered Honda Accord from a friend for my daughter. The a-arm broke the other day. They fixed it but now I'm not sure if it will break again or if it is safe to drive?

 

What do you mean by "Fixed"? JB Weld? Duct tape? chewing gum? Bailing wire or twine? Tig welded back together? Or a new or used part installed? I'd say if it was welded, get it replaced with new or used (look for any cracks in a used part)

A non-cracked used part should be just fine and would be just as safe to drive as the car was before.

Welding a vital structual part means more stresses added due to improper heat treatment and I'd expect it to fail rather soon. Tig welding or electric arc welding or torch welding literally melts the steel and when it cools, it's much harder and more brittle. Brass Brazing with a torch would not be nearly as strong and would fail soon too.

 

I agree, check what kind of welding was done, or junk yard part. I wouldn't give my daughter a part with a bad weld.