Purchasing supplies/neurotoxins/fillers/etc

Helping set up and launch a small medspa - and am confused. I thought ordering for things like RHA/Jeuveua/Sculptra etc would be done through the manufacture but I am coming across sites like Medica Depot, Pipeline Medical, Med Shift? Are these legit sources to order through? I also see Henry Schein allows you to order Jeuveau, which I know Henry Schein is legit...