temp agencies don't take anything from your pay.
here's how they make their money......
basically off percentages. you're going to be on the temp agencies payroll, not the company you're actually working at. the temp agency will charge the client (company you're working for) a certain amount of money, and pay you less than that.
say the job pays $10 per hour. they'll charge the client like $18 an hour. that covers time spent recruiting candidates, health insurance, and whatever other bills to keep you on their payroll, plus a little change so they can be profitable.
but, to answer your question, no. they're not taking a cut of your money. they're going to pay you the hourly rate you agree to for whatever job they get you.
as far as permanent gigs....no, the candidate never pays. typical recruiting fees are 20-30% of the base salary of the candidate, and the client or company you get placed in, pays for that.
100k base at a 25% fee = 25k invoice to the client.
if a recruiter ever asks you for a fucking penny, tell them to go pound fucking sand. but, if they ever get you your dream job, and are really cool throughout the whole process, they (we) appreciate nice shit like bottles of wine, or beers around the world or something. because, cool gestures like that are fucking cool.