It depends on how you want to play your business, if you want to do things by the hour like say 15-30 is what I charge. Sometimes that includes yards but only when I do additional work like detailed bush and hedge trimming and pruning, get you about 10 or so customers and they will keep you a pretty good substantial income. therefore I only have a few so I do have my construction business to hwork either way just to. back it up. But I do know if you have a mow blow and go business you will need a lot of customers
If you have the by hour, you will not exactly need a zero turn, you could have a good riding mower though and find a deal on it
You would have to invest in weed eater, maybe the attachments to the motor and ne pricing it came out to be about 300-400 for that. Pruning tools and trimming tools and a push mower. it will come out well under the 3500 mark.
Where I live you have to pay the government %15 tax
hope I could be of help