+1 for the rigid steel bikes from the late 1980s early 90s. Most of them came with decent 36-spoke wheels though many had single-walled rims but still held up well. You can pick them up in good ridable condition for <$200. Most bike shops have "used" new entry level seats in the bargain bins from people who have upgraded. I have a Bontrager SSR on the bike in the picture. It cost me $5 and looked as if it had never been sat on. I've picked up similar seats for flip bikes for $10-20. If you swap out knobby tires, you can get decent commuters like the Bontrager H2s for around $25-30 each. Of course you can spend more on higher level tires if you want.
When/if you need to upgrade wheels, you can get a machine built set with 36 straight-gauge spokes, Shimano entry level hubs, and basic double walled rims for around $250-300. I have a set of handbuilt wheels with Salsa Delgado (double-walled, eyeletted) rims laced to Shimano Deore LX hubs with DT double butted spokes that cost me less than $400 and have performed perfectly needing only very minor truing on an annual basis. I consider these a mid-level, Clyde ready wheelset.
As mentioned, well built 32-spoke wheels would likely be fine, but if you need/want to get a wheelset and want them a bit more bombproof, the weight penalty for 36-spokes is minor and the strength increase is significant (not huge, but significant).
Last edited by Myosmith; 02-28-14 at 08:25 AM.