My first inclanation was to say get insurance, but you thought of that. To begin with all you should need is GL, but you might want to look into your local laws. Competing is a very easy thing to do when you are small. With your low overhead you can keep your prices down. Being a money man already you have a step up on alot of folks. I do the same thing now, have full time arborist job, and do "side work" after work and on weekends. I started out with a pickup, saws and gear. In reading the site you probably have read the harping I do on training materials. Tree climbers companion, ISA Arborist Certification Study Guild, Arboriculture and the Law. This site is great, there are other forum sites, www.isa-arbor.com, www.sherrilltree.com. The sherrill site is a supplier but they also have some learning stuff on there too, tricks and such. Biggest thing, dont hesitate to ask a question, we are all here to help. Sometimes it gets a little dead around here and a little stimulation is what we need.