The going rate for warehouse / light industrial space seems to be ~$2-3 / sq-ft / year.
1723 McLain St (google maps street view), 1330 ft^2, $700/month, this works out to ~$6/sq-ft/year (double the rate on the slightly larger or Front St spaces). Last purchased in 2006 for 25k; should be able to negotiate significantly lower rent than they are asking.
Medium Warehouse / OfficeEdit
$3/sq-ft/year; 6700 sq-ft; $1675/month
Property purchased for 126k in 2006, payments on that sized loan would be ~1k/month depending on interest rate / down payment, may be able to talk them down a bit
949 S. Patterson Blvd. (Google maps street view)
This one is probably too big / expensive for starters, but it is an interesting possibility.