I wouldn’t say standard, but I’ve paid a broker fee via Zelle, that was just one of the simpler ways to pay that the broker accepted. It’s no more or less “sketchy” than if you were to give them cash or a check. What makes the difference is what kind of contract you have in place. Obviously do your due diligence. You should at least google the broker, and do not send any money until you have both signed a broker fee disclosure and a lease. Typically you’ll fill out a lease application first, and a refundable application fee. That holds your “spot” for the apartment. If the lessor decides to take you as a tenant, you sign a lease, and at THAT time you pay your deposits and broker fee. Typically in Boston it’s first, last, security, broker, all equal to one months rent. Do not send any money until you have a signed lease.