Necessities rhymes with:
complexities, complicities, eccentricities, niceties, universities', annuities, authorities', authority's, availabilities, banalities, causalities, cavities, celebrities, celebrity's, charities', christianity's, community's, complexities, complicities, eccentricities, entities, entities', facility's, gratuities, humanities, humanity's, identities, illegalities, immunities, indemnities, inequalities, infidelities, infirmities, insecurities, instabilities, legalities, localities, majorities, maturities, municipalities, nationalities, niceties, obscenities, personalities, principalities, rarities, rigidities, sensibilities, sensitivities, trinity's, universities', varity's, vulnerabilities
Necessities sounds like:
nacogdoches, nasdaq, nasdaq's, nast's, nastasi, naugatuck, necessitates, neckties, negates, negotiates, nest-egg, nests, newscasts, newsday's, next's, niceties, night's, nighthawk, nighthawks, nights, nights', nonjets, nonstick, nugget's, nuggets