I just went back and read most of the thread. I read the part that says your an engineer by trade doing tree work on the side. I was 4th generation in the trade and have loved the work all of my life. I know why people get hooked on this work. It's good honest WORK. It's hard, healthy, and you can make a lot of money. Here's the point where I might PO a lot of guys.
Are you LICENSED? Are you INSURED? I know everyone must get started somewhere, but doing pro tree work is not the right place to start. Since you said you were doing an apt complex I assumed you were a legal company, they usually check. If not licensed and insured, don't worry about equipment, stop now, untill you are. One screw up on your part will ruin your life forever, not to mention the lives of the people you're working for. If you're on the up and up, sorry for the lecture. When I took my MD Tree Expert exam in 1999 you had to have a 4 year degree in an arborculter related field or 8 years in the industry. I don't see where you can have the time and education to have met minimal requirements. Home improvement and business license's don't count. If you're not ISA licensed, you're not legal.
My lecture is over, now we can get back to all of the neat equipment, Joe.