2 bits of advice
My start up was about 10k.
1)The most important thing to have for your business is 5k in the Bank.
This doesnt get touched unless theres an emergency.
Its there if the truck breaks down for the second time in a week.
Its there if the phone doesnt ring for 4 weeks.
Spend money above that, pay yourself with money above that. But dont think of it as savings, but save your ass funds.
2) Treework is contextual. (so is advice)
Gear, staff and the nature of tree work that you do is unique to your situation (environment, budget, tree species, tree sizes, clients budget and property size and attitude and tree coverage, access, competitor coverage, travel distances, dumping situation, firewood demand, mulch demand, your skills and mechanical ability etc etc.)
Basically all situations are different. What works for one company would ruin another.
For example, I can count on one hand the number of times a tracked stumpgrinder would be useful or profitable for me in a year, but my stumpmaster (like an alpine magnum) gets used weekly. But for others the opposite would be true
This site is full of knowledgable guys who know what the best gear is, but only YOU will know what gear will work out for you.