Brokerage firms that solicit new agents

Hello,

I was curious about the brokerage firms that go after new real estate agents and what their business model is? Are they just raising an army so they can out compete other agencies in the market? I just got my license and have received a bunch of emails from brokers asking me to join their team. But are they actually giving me listings to show with an opportunity to make a sale/commision? I am a bit doubtful they have so many listings to show they are hiring wholesale. Has anyone on here worked with one of these agencies? One of the ones that I got an email from that grabbed my attention was RelatedISG, but mostly because of the name and I know how big and presumably well connected the Related group is.