Hi @Luis Perez, are the brokerages telling you that you need to give them $1000 to get started?
This cost could be for items that are just cost of being in the business which include, National (and local) Association of Realtor's dues, MLS dues, EKey fee's (provide you access to properties for showings) and Error and Omissions insurance. All of these costs are annual costs of doing business as a real estate agent and are typically prorated if it is not the beginning of the year. Unless the brokerage you choose decides to cover these costs you'll likely have to come up with them out of pocket.
Depending on the brokerage some of them may help you with certain costs for your first year but I wouldn't count on it. Other costs you should pay attention to are desk fee's and commission splits. Some brokerages charge both, some charge one or the other, it just depends on their business model.
RedFin advertises that they cover these costs for certain agents but I'm not sure how everything there works. Check this link out Real Estate Agent (Listing Focused). If you haven't contacted them yet it could be worth a call.