You have to consider many things when making the decision of how you will physically operate you business; environment, climate, volume, target market, efficiency, and of course funding. There is nothing wrong with operating out of your trunk, especially when youre new to the game. GSRStillez, ScottWax, AJBarnes, 1 Clean WS6, SpoiledMan (. . . .) all rock the trunk and do some of the best jobs around. While it may be confusing for a tunnel wash victim to see the detailer who is going to fix their vehicle rolls up in an Integra, all that matters is the job you do. Keep your own vehicle immaculate, dress professionally, educate yourself and your clients and work harder than you ever have before. Word will travel faster than you can imagine. M2C-HTH.
edit: That said, you might spring for a little Honda e200U generator to power your polisher/vac/etc to broaden your base.