Most medium format SLRs have a variety of viewfinders to choose from; some have built in meters, and some don't. The difference in cost between a metered prism finder and an un-metered prism finder is usually as much or more than a nice hand held meter, so I agree with the above posts that recommend getting a hand held meter.
When I went looking for a Hasselblad 500 series camera I was looking for one with a waist level finder, but I found a deal on a very clean Hassy 500c/m with a metered prism finder for about what I expected to pay for one with just the WL finder. I've never been really impressed with the in-camera meters on most of the medium format SLRs I've used, but this one seems very accurate when compared to my hand held meter. I still use the hand held meter though; it's just a lot more versatile.
You can get hand held light meters for between $50 and $100; they usually have one style of metering. Meters with more features can get expensive pretty quick. If you are going to spend a couple of hundred bucks take the time to make sure you're getting what you need now, and in the future.
I use a Sekonic 508. It has incident, spot, and flash meter built into one unit, with a few other features: memory, averaging, custom settings, etc... It was expensive at the time, but cheaper than buying 2 or 3 seperate meters to get those features. It serves me well from my landscape photography to portraits with flash.