Why should I invest my own money in racing before seeking sponsorships?

According to Corey Weller, who maxed out all her credit cards to race her first year in short course racing, you have to invest in yourself before somebody else is going to invest in you. You need to show a presence somewhere before somebody even knows who you are. By getting yourself out there and working your way through the field, sponsors can see what you're capable of. In Corey's case, this self-investment led to her first podium that year, which attracted suspension sponsor XMF and HJC Helmets who approached her directly. Companies can't sponsor you if they don't even know what you're about.