absolutely!
been down that road 2 times and will never again. they try and nickel and dime you all the way down to the friggin nails they use.
make sure everything is in writing and all the add-ons too or you'll get screwed.
all the way down to what knobs you want on your cabinets, hardware on everything, padding for the carpet, plumbing fixtures and accessories, base and crown molding, molding around your windows and doors, the type/brand of windows you are getting, the shingles for your roof, dimmer switches, size of hot water heater (you want 80 gal min), electric fixtures are expensive as hell so make sure everything is in writing. get the idea? you want the whole thing in writing so there is no arguments down the line.
don't let him sucker you into accepting a "generous allowance" for everything because you'll get fcuked like i did both times.
take your time deciding what you want because they sure as hell will take their time building the house.