"Profitable side-project" might be an unstable equilibrium. If you're doing something without scale, it will die when you lose interest. If you're doing something with scale, perhaps it should grow into a bootstrapped startup.
inquicker.com started as a hobby / learning opportunity (2005) and grew into a side project with about $20k/yr in recurring revenue from corporate customers (2008).
Eventually, it turned into a full-time job (early 2009) and I found a co-founder (late 2009). We hired our first four employees in 2010. In 2011 we signed our 100th customer and hit $1m in recurring revenue. In 2013 we hit $5m in recurring revenue.
For a rational actor, it should be an unstable equilibrium.
If you can make more profit per hour spent in your spare time that in your job, then it won't be long until you quit and spend all of you time. If not then you will give it up, unless it is just a hobby. (Hobbies might be exception to the rule)
> If you're doing something without scale, it will die when you lose interest.
I read most of patio11's advice as being about exactly this: how to build a not-necessarily-scalable business that you can lose interest in without it dying. (Namely, by contracting out content-generation and community management and treating the commissions/wages of those people as part of your user acquisition costs.)
inquicker.com started as a hobby / learning opportunity (2005) and grew into a side project with about $20k/yr in recurring revenue from corporate customers (2008).
Eventually, it turned into a full-time job (early 2009) and I found a co-founder (late 2009). We hired our first four employees in 2010. In 2011 we signed our 100th customer and hit $1m in recurring revenue. In 2013 we hit $5m in recurring revenue.