Your greatest expense may be the tower. I'd guess you will spend $1500 on a tower - or more. This makes a small turbine less than an Ideal choice. You will also have not so cheap inverters and non-free batteries (unless you bribe the beer-girl at the local golf course and liberate golf cart batteries - hint, steal the batteries - when he replaces the stollen batteries with new ones, switch his old batteries back into the golf cart.)

I will recommend a smaller turbine as a 'warm-up' project - an ~10' or so and use that experience to help you with a 17-20' mill.

And, joking aobut liberating batteries.