One word of caution though.... IF you are having a professional put in the outlet for this make sure he understands it is 120 volt and MEASURE it before you plug in (or have him measure it)
Or better yet, if having a pro do it IF you plan on leaving the outlet in place (A good idea if it is where it can be done) after house is built.. have him put in a 50 to start with and use a dog bone to connect.
Well. the cost of 50/30 now is not that much, but the cost of upgrading to 50 later... If you put in a 30 now, is great, but if you put in a 50 now, it is zero.