Am I correct in thinking that if I was to manage a sub domain for joe's butchers on my main website that if I domain map it to his url joesbutchers.com for example it would look like he had his own website on his url?
Yes - that;s how the domain mapping at Synthesis works.
If this is feasible is it still possible to add Genesis Connect and BuddyPress to it as well?
Only if you actually need those features.
This forum is for theme suport. If you have more questions about domain mapping, ask the Synthesis help desk or post in the wordpress.org forums.
These forums were CLOSED to new posts on November 19th, 2012. New forums are here: http://www.studiopress.com/forums/
and you will need to SIGN UP AGAIN.
If you need assitance with setting up your theme, go to http://my.studiopress.com/
and read the SETUP links or the TUTORIALS link on the side tab.
If you need Account Assistance
, file a help desk ticket at the same location.