I'm buying a condo, and the contract has some questionable areas, when do I hire a lawyer?

I'm about to put an offer in on a condo, but I've reviewed the contract and there are a few things that I'd like to take out or have revised. My realtor advised me to call a lawyer before making the offer in order to get his advice on the proceedings - whether to go forth with the offer and handle the legal issues during attorney review, or to go over the contract before writing up the offer...? I'm not sure what to do, as I don't presently have an attorney and I do not want to be charged prior to attorney review if I don't have to. Does anyone know the proper proceedings or have any advice as to my next step? Thanks everyone.