Mucous is the adjectival form of the more familiar noun, mucus. In other words, mucous is actually the action or ability to make the yucky stuff we blow into tissue, which is mucus. There are mucous cells, mucous fluid, mucous membranes, and mucous glands. They are all different objects that can secrete mucus.
  Thus, if you have business income, you can contribute to your ROTH IRA if you are eligible and a SEP IRA. If your SEP IRA is likely to become substantial or you have funds in a 401(k) from a previous employer and you are an one person (or one person with a spouse) business, you should look into individual 401(k)s.
Different rules apply if you are trying to combine your SEP IRA and a Roth 401(k) plan. You're not allowed to transfer money from a SEP IRA directly into a Roth 401(k) plan, even if you pay taxes on it at tax time. But, you are allowed to transfer money in a 401(k) plan to a Roth 401(k) plan.