I was laid off from my job recently and I am considering becoming a
real estate agent.  Is it legal to collect unemployment as a real
estate agent until I receive my first commission check?

Is there any reason you don't just ask your state's dept. of
labor/unemployment bureau?

I don't know the laws of all states, but when I worked for the
Oklahoma Employment Security Commission, wages and other payments were
to be reported on the date when they were earned, not the date when
the check arrived. Failing to report earnings while drawing
unemployment compensation can result in criminal prosecution.