Agents should never charge before they find you work.
If you feel like someone is trying to get you to pay an upfront fee- then its a scam. If they are trying to convince you to pay their photographer to take your pictures- then its a scam. If you hear an agency who constantly talks about how unique your look is, beware.
On average their rate is approximately 10% of what you earn. Managers usually earn a bit more, sometimes up to 20%. It seems like it would be easier to choose to get an agent, but agents are a lot harder to get than a manager.
Look up reviews on everyone before you pay them. Read the bad reviews and analyze the business to see if it is worth spending your money.
A lot of people and their companies scam actors and do not think twice about it.
If someone is excessively friendly and pushy to sell to you, it is because they are scamming you.