If you are going to work in the city, and not rural areas, you need to learn the business. It's more than just chainsaws and falling. I would suggest you get a job as a groundie somewhere and learn how the business works. You can learn how jobs are bids, (not just the $ but what to look for), how jobs are done, equipment requirements (both large and small equipment), how debris is dealt with and how you get paid.
Once you have been on jobs for a while, you can decide whether you want to concentrate on removals (requiring a higher investment in equipment and skill, but a lower investment in knowledge) or pruning/tree care (requiring more knowledge but less equipment).
Once you are working for someone, you may decide to do side jobs on weekends. This will teach you how to deal with customers and bid jobs.
It's no longer a business/profession you can just throw your shingle up and people will come to you. In most cities you will be fighting lots of established competition.
Good luck.
