I'm assuming you're in the US. If you're not, disregard and refer to the laws in your country.
DX 5 - well, those things are labeled such that they are legal to own, but be warned that they are often not in spec. The 2 that I have owned/used are both too bright to really use in situations like presentations in dark rooms or classrooms. They're not great quality control, and it may not be worth the hassle of trying to sell them to others. If you do, make sure they know what they're getting (could die at any time, not necessarily true output, not great quality control, etc.). My last DX True 5mW, for example, has its beam coming out at an angle about 20 or so degrees off of straight forward. Doesn't matter to me, but it may to people you sell it to.
DX 30 - You can if you want, but be forewarned, this this is illegal. Anyone telling you "oh, it's ok, you won't get caught" isn't giving you legal advice, and keep that in mind. These lasers are illegal to import into the US, and illegal to sell in the US. Again, you can if you want to, but it's up to you how much risk you want to take with breaking the law. Personally, I would rather you didn't, because 1 incident of a lack of judgment with a laser might be all it takes for that 1 lawsuit or 1 tragic accident that makes lasers, as a hobby, illegal for ALL of us. And young people with easy access to lasers (apparently they don't have access to them over DX now?) and who don't understand the risks/consequences of these things are the ones most likely to make such mistakes and make life hard for all of us.