Stable income: Somewhat stable

Bike renting can be a moderately stable source of income for most people who try it. From online sources and personal experience, it seems that individuals can earn consistently, although there may be some variability depending on factors like location and season. Setting up a bike rental business typically costs from $500 to $2,000. If your best friend quit their job to do this full-time, you could say, 'You'll be fine,' as long as they are prepared for some fluctuations in income. I'd rate it a 3 out of 5 because while there is decent baseline income, there can be some unreliability at times.