It is possible to host six or unlimited domains under your reseller hosting account within the resources allocated to you. You can host these domains as separate individual hosting accounts in server so that they will not come under the main reseller public_html directory avoiding any confusion. They will be treated as any other individual accounts in server but owned under main reseller account. You can create this accounts through WHM of main reseller account. As an alternative to this you can go for the addon domain feature in cpanel but I would recommend the latter as it avoid confusion regarding home directories of each domain.