Or search: pupil, renter, tenant, lodger, roomer, intruder, trespasser
2 Syllables: SU
border, coarser, corner, courtier, foreigner, Foreword, former, Forster, forward, horror, mortar, mourner, northern, northward, orchard, order, porter, Puerto, quarter, shorter, torpor, torture, warmer, Warner, warrior, Yorker, Yorkshire
3 Syllables: USU
disorder, explorer, exporters, henceforward, importer, informer, performer, recorder, reformer, reporter, restorer, straightforward, supporter, thenceforward, threequarters, transformer

Found 43 words across 2 groupings. Skipped 31 excess words of a similar stem.