Before starting a business, the questions that matter are whether anyone has actually paid you yet, how much capital you can lose without it hurting, whether you go full-time or build alongside a job, and on what written terms you work with a co-founder. Most businesses do not fail from a bad idea — they run out of money or patience first. A co-founder arrangement with no written equity split, vesting or exit clause is among the most common ways a working business dies, and deciding in advance what would make you stop is the difference between a business and a slow drain.