Some even have the capital only through word of mouth and started with commissions until they have developed a system. It all it takes is some guts, a few capital to none and a simple plan. Just follow what the famous trademark of Nike is, 'just do it'.
It boils down to that.
Worth mentioning is that alone its way harder to raise.
Have a team, many start ups are friends who had the idea and the willpower.
The business plan on a start up is necessary to raise capital.