If no one has mentioned already, No legitimate company asks for an upfront feee for anything.
If they do ask for an upfront fee,Walk away as all they are doing is making a quick buck.
Real companies as I have mentioned before, they don't ask for upfront fee's as it is their priviledge of show casing their company and subsequently hope to recruit a new model if the person in question is happy to join.
Real companies take the hit for any costs as they can pass the cost onto whatever company they are going to be workign with.
So basically, portfolio cost shouldn't be ask for by a company .
Sign up fee shouldn't be ask for as there is no such cost to sign up.