If you have joined a startup or thinking of joining one and don't know much about the startup world, then this little advice is for you. Beware co-founders... :) This is for start-up employees strictly.
We hear all the time on internet news about startups that got funded in millions. What we don't hear are the hundreds of startups that tried and did not quite make it. There are many reasons for a startup for fail.

1. An idea that does not solve a real world problem.
2. An idea that has a temporary value.
3. A team incapable of executing the idea.
4. Incorrect approach to solving a problem.
5. Overspending

and the list goes on...

Chances are that you are joining a startup because of an incentive either in form of better salary or an equity. There is a higher risk involved and it makes sense to be compensated better than a similar position at an established organization.

So, I learned this the hard way, when I joined a startup for a good compensation and dropped all side projects, part-time work because I thought now I didn't need to. Six months into the job, the startup burnt all the cash and I was without work and money. The idea isn't to do lesser at your full-time job, but it is of having a side income, in case things don't work out well for the startup. Do the following in order to make your finances safe:

1. Stay in touch with old employers, clients at good terms.
2. Keep working on small side project and maintain a steady pipeline of work.
3. Keep learning.
4. Know your capacity.