Can I build a duplex in Orion Township?

Not in the single-family districts. The use matrices for SF, SE, SR, R-1, R-2, and R-3 list single-family detached dwellings and never mention two-family dwellings (Section 5.01; Section 6.01). The ordinance defines a two-family dwelling or duplex in Article II, but the only districts whose use lists include 2-plex units are the multiple-family districts.

In RM-1 and RM-2, multi-family dwellings including 2-, 3-, and 4-plex units are permitted by right (Section 7.01). The catch is scale: a multiple-family development needs a site of at least 5 acres, density is capped at 6 units per acre in RM-1 and 8 in RM-2, and site plan approval applies (Section 7.03.B; Section 7.04.C; Section 30.01).

So a one-off duplex on a typical residential lot would need a rezoning to RM, a PUD approval under Section 30.03, or a use variance, all discretionary. If your parcel is near an RM district boundary or a major corridor, ask Planning & Zoning at 248-391-0304 ext. 5000 what the master plan supports before spending on design.