Backstairs rhymes with:
airfares, americares, armchairs, bankshares, daycares, delaware's, fiduciares, forebears, healthcare's, housewares, legionnaire's, legionnaires, markair's, medicare's, nightmares, software's, somewheres, tenncare's, thoroughfares, wheelchairs
Backstairs sounds like:
babysitters, backdoors, backstroke, backtrack, backtracks, backwaters, bacteria's, bastarache, baxter's, boisterous, bookstores, booster's, boosters, busters