I'm a professional property manager. As part of the listing process I naturally do rental comparables. If you are interested in using a property manager to rent your townhouse, I'd be happy to help you with comparables.
FYI, although using an appraiser for such a thing would be effective, and potentially very comprehensive...it would also be very expensive. Typical appraisal fees are very close to the entire commission I charge to rent the home for a year, which INCLUDE my estimate of rental rates...and from someone that has successfully rented 40 homes this year alone.
FYI, the hassle with craigslist (and I wouldn't ignore craigslist), is that it's not a very location specific search. If there are listings in your townhome community, you will probably find them, but what about the next community over, or down the street, or around the corner. It's brutal (not impossible, but tedious) to use craigslist to find rental comparables for homes within a mile or two, which is part of what you want in the analysis. Also, you never know what it actually rented for, just what the asking price was.