I have done my research and have found many multi-family units currently available in the Las Vegas area. Prices for 4 unit buildings seem to range from anywhere around $1,400,000 for the very classy units, down to about $250,000 for less desirable properties.
For example, there is a high-end 4 unit complex with two 2br/2ba and two 2br/1ba units around the Hwy 15 and East Tropicania Ave area. It is currently listed at $1.4M and is listed by Victoria Lackey of Members Real Estate Services.
For something less expensive but still relatively nice is a 4 unit with four 1br/1ba units going for $695,000. This property is located around the Hwy 15 and 515 area. It is listed by Century 21, and I have noticed they do have several other multi-family units currently listed as well.
If you are looking for something that is going to cash flow I would suggest taking a look at some of the several four units currently available in the $300,000 price range. My top pick after doing some research would probably be a property located at 771 Palo Verde Cr currently going for only $290,000. This property has a total of 4576 sf and features 5 units. It has one 1br/1ba unit, two 2br/1ba units, one 3br/1ba unit and one 3br/2ba unit. Seems like this property would cash flow very nicely and is currently listed with Alliance Properties.
If you are looking for a good resource for more properites I would consider going to realtor.com because they have many multi-family properties listed there.