Damn dude, if you're into medium format the Mamya 6 is a sweet camera... assuming it's the modern one... there's a really old one with a fixed lens that I know nothing about.
It's a rangefinder camera because that takes out a lot of weight and vibration... it shoots a little sharper than an SLR. Mamiya glass is is top quality. What lens is on it?
The thing about MF is that it's film and you have to have a lab that will process and print for you unless you want to go the home darkroom route.
The camera body without lens looks like it sells used in good condition for $700 to $900, with an 80mm lens... probably $1100 - $1300. To sell it on ebay you'd get between 60% and 80% of that depending on the camera's condition, which lens it has and how you were holding your tongue when you listed it.
What makes that camera special is it's size and weight, it's very compact for an MF camera. Mamiya is a top tier maker. The thing is, if you're not seriously into photography (I mean geek serious) and you own a digital camera... you're not gonna shoot it much. It's just so much more involved getting the images in print or digital format.
If it was me, I'd do the job because I collect cameras... but I'd still shoot my digital Nikon most of the time.