Rs 10,000-20,000 for an entry-level kit (balloon pump, stands, basic colour balloons, simple backdrop material), per OkCredit's India balloon-decoration-business cost guide. A Mudra Shishu loan (up to Rs 50,000, collateral-free) can fund a bigger starter kit including flower-decor add-ons.
No independently verified per-event pricing data was found for solo decorators in India, so use local competitor pricing in your town as your benchmark; the category has demonstrated room to scale -- branded operators like The BalloonWala have grown from a similar starting point into recognized city-wide businesses.
Figures are quoted from the sources listed under Useful resources on this page. Check them against current local prices before you rely on them.