Rental programs are quitting-insurance that quietly costs 2–3× the instrument. Find your break-even before you sign.
First year of a maybe-committed beginner (quitting insurance is real — about half of beginners stop within two years). Fractional-size strings (violin/viola/cello) where the child outgrows 2–3 sizes — rental size-swaps beat re-buying. And school-owned rarities (oboe, bassoon, French horn, tuba) — ask the band director before renting anything expensive.