I would agree with a few others on a few points. 1. A new humidor is typically going to be lined with a Spanish cedar as a means of keeping rh stable. While this won't necessarily funk up your mj taste after the humidor is well seasoned, it might so beware. I wouldn't go out and buy an expensive humidor for mj unless you've tried it and like it. 2. Wouldn't suggest mixing cigars and mj for a few reasons. One is that cigar tobacco is generally fermented. Like mj, you need to "burp" the storage container occasionally to release some of the gases that will continue to escape after curing. Good cigars are cured before you buy them and are aging in your humidor at a specific rh and temp range to slow down that curing/fermenting. The rh and temp range aren't vastly different than for mj, but you risk either over-drying your cigars or over-moistening your mj. Also not sure if any gases or impurities (mold, fungus) may develop and spread from cigar to mj or vv. wouldn't want to risk my good cigars or my mj.
3. Like others have said, hang dry or back in the day we used to use brown paper bags in a cool dark place to slowly dry and cure. A mason jar works just fine but an opaque container may be preferable, or just keep the jar in a dark place. You could build a mj humidor without cedar with contents-specific rh and temp but wouldn't use it for both cigars and mj. I've heard a jar in a wine cooler works quite well, and you can buy the humidifier / humistat and out it in a non- cigar non-cedar humidor device (even a cooler), just make sure to burp occasionally to let gases out and whatever you use as a humidification agent make sure you use distiller water or some of the rh beads or crystals (you can buy beads or crystals that are set to maintain a specific rh), not tap water or orange peels or crap like that if you want to avoid introducing mold and bacteria. Sterile is much safer. Monitor for rh and mold carefully.
I have a nice humidor but it's for cigars. For mj, unless you're keeping a long time, any sealed sterile container will work, dark is better, and if your climate requires humidification or drying for long term storage, keep it sterile and avoid cedar, tobacco and plan to check or monitor rh at least weekly when you burp the container.