is freelance work legal for F1

A local Architecture company wants me to photography their finished
projects.Photography is my hobby,and my major is not related to this but i have
minor in Architecture,this task is based on each project and i get paid by
finishing each of them,freelance work. Now i am worried about if it is legal to
do so,i have F-1 visa,one of my friend said it is not job,but i want to make
sure before i begin to do it. Since the boss is American,i am afraid that if i
require paid by cash,he will not let me do it. But if i deposit their firm
check,i will leave the record on my bank,do you know how i can handle this?Any
suggestion is highly appreciated!