It would be something you'd need to discuss with a potenital broker.
I've learned my lesson with not asking enough questions on that, i went with a high profile company for one of my domains, i could say lots of things how poor and unprofessional they was, but basicly in a nutshell, just sat on domain, did nothing and even ignored my e-mails chasing up asking for updates.
Problem is once you sign a contract with one of these brokers, that's it, you can't do anything yourself with your own domain for usually 6 months, some even want ties to your domain (in some shape or form) even after the term of the contract is over and representation as ended, read through the terms of the contract on things like that.
Discuss with a potenital broker the plan for selling your domain. If you are happy with what they say, go for it, if not, stay away, I know i personally will never go with a broker again usless:-
1) It's a broker who primarly targets end-users (ie using their contacts on LinkedIn/eMailing companies or phoning potenital buyers up), not doing something what i can do and advertising the domain on NamePros.
2) Gives updates at least once a month what they've been doing to sell the domain.
3) There's a get out clause (no questions asked) for both parties after 2 months, i think after 2 months both broker and domain owner will know if they are the right person to represent the domain or not.