How's the Natural Ambiance?
Even small touches of nature can enhance an urban townhome, and those can come in a couple of forms. End units often have a little more outdoor space, like extra elbow room in the yard or an added porch or patio. But if a townhome you're considering is sandwiched between two others instead of being the slice of bread on either end, then having a little outdoor haven is a great plus. Your yard will, however, probably have to be sparingly luxurious given that townhouses don't tend to have much real estate beyond the building's footprint.
Look for a nice solid fence out back – make sure it's good and sturdy. Ask about any encroaching hedges and overhanging trees: Whose responsibility are they? A nicely landscaped setting is a plus, unless gardening is one of your primary hobbies, in which case an unfinished yard can provide you with plenty of pleasant afternoons over the next couple of years while you beautify it.
Thanks to their shared walls, most townhomes have windows only in the front and back, not on the sides, so overhead skylights are another great way to welcome the natural world into your future home. If the unit doesn't have any, find out if you can install some. Be wary of potential neighbors who have a complete disregard for light pollution, though. In close quarters like these, anyone who likes to crank the watts late at night could do some serious damage to your sleep cycle.