Hey, now. Don't get discouraged before you even start.
Zam is a super hard costume to do with tons of intricate parts. We just don't want to see you sink your money into something that you can't use to become part of the 501st. Considering the cost of building a Zam on your own is somewhere north of $3,000-$3,500, I have to imagine that having someone build it for you to 501st specs--especially as quickly as in a month--would cost at least $6,000-$7,000, if not more. If she's doing it much cheaper than that, I'd just be very attentive to whether it will be 501st approvable. If she's an experienced 501st costumer, she knows that drill already.
Different people go about this different ways. Sometimes they have a specific costume that they want to do no matter what, and they take all the time they need (sometimes years--literally) to build it. Other people just want to get involved quickly, so they opt for a pilot or jedi or something that's mostly soft parts to start out. Once you're exposed to more costuming stuff and people here with all their skills, you'll learn more about how to build things, when it's better to do it yourself, when it's better to pay someone else to do it, etc. Once you've been through an approval process, you'll be more familiar with how that whole process works and how important the CRLs are.
This hobby is a huge learning process, and that part of it is a lot of fun. You just have to figure out what works best for you!