Hello Alice, welcome to the Mayhem

...... Oo I'm tired I wrote all the stuff in green and then realised you said 'building' not 'buying'

I imagine we would need a little more info in order to get you started.... Eg, have you got any model building experience? Have you got the basic amount of tools and do you have somewhere to build it?
Each of these questions points to a new set of questions but will help determine a start point. No one wants to put off a beginner with in depth detail just as no one wants to talk really basic to someone with building experience.
This is the best place to get advice, not only that but there is a good chance that someone will probably have just what you are looking for and all the advice to go with it. Failing that someone will know of your nearest club, or shop or mayhemmer who can sell you one with confidence.
A couple of things to think about.
Do you already have radio equipment or do you need that as well? (Possible extra expense)
Think about transporting it to and from your place of sailing. (Can you transport it already set up or will it not fit in your car?) even small yachts can be tall when sitting on a stand.
I'm sure you will get what you need ..... Good luck and happy sailing..... U2