This.
If they offer stuff like sealing the ductwork, or other energy saving stuff, get that done now because you'll never be able to do it again. Consider insulating bedroom walls for noise. Run network cable to every room. Since its a townhouse, male sure the firewall between units is being done correctly. Some idiot builders will put an electrical outlet in the same concrete block for both units, so you've effectively ruined the whole fire rating of the wall. Not to mention noise/smells.