I have been building a bootstrapped SaaS business for the better part of a year working late into the night most nights per week. I have never spent anything aside from my own time and a few negligible expenses to get this system where it is now. Now that I am gearing up to launch my SaaS to the public, I need to start hiring out certain things like logo design, mobile add-ons, etc., as well as prepare to accept recurring payment for monthly services.
As I live in California, what steps must I take to "do it the right way" from a business/legal/financial perspective if I plan on continuing to be the only person working on this project?
I am doing the exact same thing as you are doing: taking an idea to a bootstrap SaaS to be beta launched in the months to come. Few resources that really helped me with graphical design, templates is the "Envato Marketplaces". It's a collection of centrally owned market websites to adhere to several needs of web entrepreneurs. They offer excellent web templates, code snippets, forms, videos, and even music soundtracks for that "demo" video many web applications need to have today to capture attention.
http://themeforest.net/ - That is the "Web Themes" landing page. Scroll down to see the types of services they offer.
Regarding logos, I recommend http://99designs.com/ - which is an online marketplace where designers and potential customers meet. You define the work you need, set a price (typically $200 and up) and literally dozens of professional designers compete for your money, suggeting you logo drafts for you to choose. When you pick the winning design, the designer gets paid.