Bootstrapping has some inherent disadvantages: you're working to pay the rent at the same time you're trying to build a successful product, so you have less time to accomplish what you really want to do, and less financial resources overall.

But if you can overcome these obstacles using proper time management, project scheduling and keeping fixed costs to a minimum, you'll end up with significantly greater equity and fewer fingers in your proverbial pie, in contrast to giving up equity and answering to your investors, however useful their input may be.

Bootstrapping a startup requires you have a real-world business model which actually generates revenue, which is more than many investor-backed companies can say. However, a profitable model is not necessarily a sustainable one. You could fill your schedule with client-contracted work and pay the monthly overhead and maybe yourselves too, but it's not the most sustainable long-term business strategy (unless you really want to be doing this forever.)

So you contract/consult to pay the bills, at the same time devoting a reasonable portion of your time to building your own products and looking for your "homerun."