Actually there is something that can be referred to as a detached condo/townhome and they are becoming more prevelent. The lots are too small for SFR setback rules, the front yards are owned and sometimes maintained by the association, but they are not attached. A lot of alley homes/shared driveway homes are technically a condo or hybrid. If the lot is smaller than 4k sq. ft. the odds are it is a detached condo.