Honestly, I am not sure where to start, I'm looking at getting into medium format, and I'm trying to figure out what I would like to get, right now I'm thinking an Mamiya RB67 would be nice, however it can be a little pricey, but it has the ability to change the film back, and I plan on shooting b&w and color film in this camera. This will be my first step into medium format, so I really don't want to spend a fortune on gear, I can follow a manual to learn how to operate a camera. I'm also considering the Mamiya M645 1000s or 645e, both seem to be cheaper than the RB67. Looking for some guidance on what to get, the camera will be used for both landscape/building type photography and portraits. I'm open to other options, I think my max budget might be $500, but being under budget would be a bonus. Thanks for any guidance provided.